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John P. R. David - One of the best experts on this subject based on the ideXlab platform.
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Avalanche Multiplication and Excess Noise in InAs Electron Avalanche Photodiodes at 77 K
IEEE Journal of Quantum Electronics, 2011Co-Authors: Andrew R. J. Marshall, Pin Jern Ker, John P. R. David, Peter Vines, Chee Hing TanAbstract:The findings of a study of impact ionization, Avalanche Multiplication and excess noise in InAs Avalanche photodiodes at 77 K are reported. It is shown that hole impact ionization is negligible in practical devices which continue to operate as electron Avalanche photodiodes, as they do at room temperature. A new electron ionization coefficient capable of modeling Multiplication at 77 K is presented and it is shown that significant Multiplication can be achieved in practical devices without excessive tunneling currents. The characteristic changes observed between room temperature and 77 K are discussed. This paper helps to demonstrate the potential for practical InAs electron Avalanche photodiodes, operating cooled.
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Nonlocal impact ionization and Avalanche Multiplication
Journal of Physics D: Applied Physics, 2010Co-Authors: G J Rees, John P. R. DavidAbstract:Impact ionization and Avalanche Multiplication are conventionally described in terms of ionization coefficients which depend only upon the local electric field. Such a description takes no account of the effect of ionization dead space, within which the population distribution, and hence the ionization coefficient of carriers injected cool approach equilibrium with the high electric field, inhibiting ionization and reducing Multiplication. This effect, which increases in importance as device dimensions are reduced, clearly benefits such high field devices as transistors by suppressing parasitic Avalanche Multiplication. It also improves the performance of Avalanche photodiodes (APDs) by reducing the spatial randomness of impact ionization, so that the resulting excess Multiplication noise is also reduced. It reduces temperature sensitivity and may also further enhance APD speed. This paper reviews these effects and some theoretical models used to describe them.In memory of Peter Robson, who inspired and encouraged scientists and engineers, young and old.
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Modeling of Avalanche Multiplication and excess noise factor in In0.52Al0.48As Avalanche photodiodes using a simple Monte Carlo model
Journal of Applied Physics, 2008Co-Authors: S. C. Liew Tat Mun, Andrew R. J. Marshall, Chee Hing Tan, Y. L. Goh, John P. R. DavidAbstract:A simple Monte Carlo model has been developed to simulate the Avalanche Multiplication process in In0.52Al0.48As. The model reproduces Avalanche Multiplication and excess noise factor measured on a wide range of In0.52Al0.48As p+-n-n+, n+-n-p+, and p+-n+ diodes and confirms that very low excess noise factor can be obtained using pure electron injection in very thick diodes with Avalanche region greater than 2.21 μm or in very thin diodes with Avalanche region lesser than 0.11 μm. In addition we investigated the effect of an electric field gradient in the Avalanche region of Avalanche photodiodes and found that the excess noise factor can be reduced with electric field gradients. However in thin diodes with Avalanche region lesser than 0.20 μm, the onset of tunneling current negates the excess noise reduction achieved using the electric field gradient. Therefore ideal p+-i-n+ diodes still provide the overall preferred structure.
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Avalanche Multiplication and Impact Ionisation in Separate Absorption and Multiplication 4H-SiC Avalanche Photodiodes
Materials Science Forum, 2008Co-Authors: Wei-sun Loh, John P. R. David, Stanislav I. Soloviev, Ho-young Cha, Peter Micah Sandvik, C. Mark JohnsonAbstract:The hole dominated Avalanche Multiplication characteristics of 4H-SiC Separate Absorption and Multiplication Avalanche photodiodes (SAM-APDs) were determined experimentally and modeled using a local Multiplication model. The 0.5x 0.5mm2 diodes had very low dark current and exhibited sharp, uniform breakdown at about 580V. The data agree with modeling result using extrapolated impact ionization coefficients reported by Ng et al. and is probably valid for electric fields as low as ~0.9MV/cm at room temperature provided that both the C-V measurements and electric field determination in this work are correct. The packaged devices demonstrate a positive temperature coefficient of breakdown voltage for temperatures ranging from 100K to 300K which is a desired feature for extreme environment applications.
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Avalanche Multiplication in InAlAs
IEEE Transactions on Electron Devices, 2007Co-Authors: Y. L. Goh, Andrew R. J. Marshall, John P. R. David, Chee Hing Tan, G J Rees, D.j. Massey, Mark Hopkinson, S.k. JonesAbstract:A systematic study of Avalanche Multiplication on a series of In 0.52Al0.48As p+-i-n+ and n +-i-p+ diodes with nominal intrinsic region thicknesses ranging from 0.1 to 2.5 mum has been used to deduce effective ionization coefficients between 220 and 980 kVmiddotcm-1. The electron and hole ionization coefficient ratio varies from 32.6 to 1.2 with increasing field. Tunneling begins to dominate the bulk current prior to Avalanche breakdown in the 0.1-mum-thick structure, imposing an upper limit to the operating field. While the local model can accurately predict the breakdown in the diodes, Multiplication is overestimated at low fields. The effects of ionization dead space, which becomes more significant as the intrinsic region thickness reduces, can be corrected for by using a simple correction technique
Guofu Niu - One of the best experts on this subject based on the ideXlab platform.
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Substrate current based Avalanche Multiplication measurement in 120 GHz SiGe HBTs
IEEE Electron Device Letters, 2003Co-Authors: Jun Pan, Guofu Niu, Jin Tang, Alvin J. Joseph, Yun Shi, David HarameAbstract:A new substrate current-based technique for measuring the Avalanche Multiplication factor (M - 1) in high-speed SiGe heterojunction bipolar transistors (HBTs) is proposed. The technique enables M - 1 measurement at high operating current densities required for high-speed operation, where conventional techniques fail because of self-heating. Using the proposed technique, M - 1 was measured up to 10 mA//spl mu/m/sup 2/ on SiGe HBTs featuring 120 GHz peak f/sub T/ which occurs at J/sub C/ about 7 mA//spl mu/m/sup 2/. Implications for circuit applications are also discussed.
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measurement of collector base junction Avalanche Multiplication effects in advanced uhv cvd sige hbt s
IEEE Transactions on Electron Devices, 1999Co-Authors: Guofu Niu, John D. Cressler, Shiming Zhang, U. Gogineni, D AhlgrenAbstract:This paper presents measurements of the Avalanche Multiplication factor (M-1) in SiGe HBTs using a new technique capable of separating the Avalanche Multiplication and Early effect contributions to the increase of collector current with collector-base bias, as well as allowing safe measurements at practical current densities. The impact of collector doping, current density, Ge profile, and operation temperature are reported for the first time using measured and simulated results from a production quality UHV/CVD SiGe HBT technology. Limitations of the technique in the presence of significant self-heating are discussed. By turning on the secondary hole impact ionization, we revealed the difference in impact ionization between strained SiGe and Si in the presence of the "dead space" effect. Despite its smaller bandgap, the compressively strained SiGe layer shows an apparent decrease in the secondary hole impact ionization rate compared to Si.
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Measurement of collector-base junction Avalanche Multiplication effects in advanced UHV/CVD SiGe HBT's
IEEE Transactions on Electron Devices, 1999Co-Authors: Guofu Niu, John D. Cressler, Shiming Zhang, U. Gogineni, David C. AhlgrenAbstract:This paper presents measurements of the Avalanche Multiplication factor (M-1) in SiGe HBTs using a new technique capable of separating the Avalanche Multiplication and Early effect contributions to the increase of collector current with collector-base bias, as well as allowing safe measurements at practical current densities. The impact of collector doping, current density, Ge profile, and operation temperature are reported for the first time using measured and simulated results from a production quality UHV/CVD SiGe HBT technology. Limitations of the technique in the presence of significant self-heating are discussed. By turning on the secondary hole impact ionization, we revealed the difference in impact ionization between strained SiGe and Si in the presence of the "dead space" effect. Despite its smaller bandgap, the compressively strained SiGe layer shows an apparent decrease in the secondary hole impact ionization rate compared to Si.
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Collector-base junction Avalanche Multiplication effects in advanced UHV/CVD SiGe HBTs
IEEE Electron Device Letters, 1998Co-Authors: Guofu Niu, John D. Cressler, U. Gogineni, David HarameAbstract:The collector-base junction Avalanche Multiplication factor (M-1) in SiGe HBTs is investigated using a new technique better tolerant to self-heating and collector-base leakage. The new technique provides higher accuracy at low current densities and enables M-1 to be measured at high current densities typically used in circuits. Comparisons with identically processed silicon control devices show that M-1 is not inadvertently increased by the incorporation of SiGe, despite its smaller bandgap. With cooling, M-1 first increases, and then saturates when T
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Photo effect based Avalanche Multiplication measurement in highly scaled SiGe HBTs
2003 Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems 2003. Digest of Papers., 1Co-Authors: Jun Pan, Guofu Niu, Jin Tang, Alvin J. Joseph, David HarameAbstract:A new photo effect based technique for measuring the Avalanche Multiplication factor (M - 1) is proposed. The technique enables M - 1 measurement at high operating current densities required for high speed operation, where conventional techniques fail because of self-heating. Using the proposed technique, M - 1 was measured up to 24 mA//spl mu/m/sup 2/ on SiGe HBTs featuring 120 GHz peak f/sub T/. Implications for circuit applications are also discussed.
John A. Rowlands - One of the best experts on this subject based on the ideXlab platform.
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Avalanche Multiplication in amorphous selenium and its utilization in imaging
Journal of Non-crystalline Solids, 2008Co-Authors: A. Reznik, Kenkichi Tanioka, Oleg Rubel, Safa Kasap, Y. Ohkawa, S. D. Baranovskii, K. Jandieri, Misao Kubota, John A. RowlandsAbstract:Abstract Amorphous selenium (a-Se) is a well known photoconductor that is currently used in X-ray image detectors and HARP video tubes. Recent advances have made it practical to operate a-Se at extremely high electric fields F , where Avalanche Multiplication occurs. At sufficiently high fields, the effective quantum efficiency ( η ∗ ) (or the overall yield) of the photoconductor can be increased several orders of magnitude above unity and renders Avalanche a-Se photoconductors a prospective alternative to vacuum photomultiplier tubes (PMTs) and silicon Avalanche photodiodes (APDs). In this work we report our study of η ∗ and charge transport for a-Se Avalanche photoconductors with different photoconductive layer thicknesses in wide range of F . Our study shows that a-Se is able to produce a gain of ∼1000 with a rise time of ∼1 ns, both of which clearly point to the potential (or realized) use of this photoconductor in a variety of imaging applications. Furthermore, our work supports the validity of the so-called modified Lucky drift model to explain the nature of impact ionization and Avalanche in this material.
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X‐ray imaging using Avalanche Multiplication in amorphous selenium: Investigation of intrinsic Avalanche noise
Medical physics, 2007Co-Authors: Dylan C. Hunt, Kenkichi Tanioka, John A. RowlandsAbstract:The flat-panel detector (FPD) is the state-of-the-art detector for digital radiography. The FPD can acquire images in real-time, has superior spatial resolution, and is free of the problems of x-ray image intensifiers-veiling glare, pin-cushion and magnetic distortion. However, FPDs suffer from poor signal to noise ratio performance at typical fluoroscopic exposure rates where the quantum noise is reduced to the point that it becomes comparable to the fixed electronic noise. It has been shown previously that Avalanche Multiplication gain in amorphous selenium (a-Se) can provide the necessary amplification to overcome the electronic noise of the FPD. Avalanche Multiplication, however, comes with its own intrinsic contribution to the noise in the form of gain fluctuation noise. In this article a cascaded systems analysis is used to present a modified metric related to the detective quantum efficiency. The modified metric is used to study a diagnostic x-ray imaging system in the presence of intrinsic Avalanche Multiplication noise independently from other noise sources, such as electronic noise. An indirect conversion imaging system is considered to make the study independent of other Avalanche Multiplication related noise sources, such as the fluctuations arising from the depth of x-ray absorption. In this case all the Avalanche events are initiated at the surface of the Avalanche layer, and there are no fluctuations in the depth of absorption. Experiments on an indirect conversion x-ray imaging system using Avalanche Multiplication in a layer of a-Se are also presented. The cascaded systems analysis shows that intrinsic noise of Avalanche Multiplication will not have any deleterious influence on detector performance at zero spatial frequency in x-ray imaging provided the product of conversion gain, coupling efficiency, and optical quantum efficiency are much greater than a factor of 2. The experimental results show that Avalanche Multiplication in a-Se behaves as an intrinsic noise free Avalanche Multiplication, in accordance with our theory. Provided good coupling efficiency and high optical quantum efficiency are maintained, Avalanche Multiplication in a-Se has the potential to increase the gain and make negligible contribution to the noise, thereby improving the performance of indirect FPDs in fluoroscopy.
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X-ray imaging using Avalanche Multiplication in amorphous selenium: Investigation of depth dependent Avalanche noise
Medical physics, 2007Co-Authors: Dylan C. Hunt, Kenkichi Tanioka, John A. RowlandsAbstract:The past decade has seen the swift development of the flat-panel detector (FPD), also known as the active matrix flat-panel imager, for digital radiography. This new technology is applicable to other modalities, such as fluoroscopy, which require the acquisition of multiple images, but could benefit from some improvements. In such applications where more than one image is acquired less radiation is available to form each image and amplifier noise becomes a serious problem. Avalanche Multiplication in amorphous selenium (a-Se) can provide the necessary amplification prior to read out so as to reduce the effect of electronic noise of the FPD. However, in direct conversion detectors Avalanche Multiplication can lead to a new source of gain fluctuation noise called depth dependent Avalanche noise. A theoretical model was developed to understand depth dependent Avalanche noise. Experiments were performed on a direct imaging system implementing Avalanche Multiplication in a layer of a-Se to validate the theory. For parameters appropriate for a diagnostic imaging FPD for fluoroscopy the detective quantum efficiency (DQE) was found to drop by as much as 50% with increasing electric field, as predicted by the theoretical model. This drop in DQE can be eliminated by separating the collection and Avalanchemore » regions. For example by having a region of low electric field where x rays are absorbed and converted into charge that then drifts into a region of high electric field where the x-ray generated charge undergoes Avalanche Multiplication. This means quantum noise limited direct conversion FPD for low exposure imaging techniques are a possibility.« less
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Sci‐Fri PM Imaging‐03: Avalanche Multiplication in diagnostic x‐ray imaging
Medical Physics, 2006Co-Authors: Dylan C. Hunt, Kenkichi Tanioka, John A. RowlandsAbstract:The state‐of‐the‐art detector for digital radiography, the flat‐panel detector (also know as the active matrix flat‐panel imager), requires more gain to improve its performance at typical fluoroscopy — real time x‐ray imaging — exposure rates. It has been shown that Avalanche Multiplication gain in amorphous selenium (a‐Se) can provide the necessary amplification. This amplification, however, must also make little or no contribution to the noise. To achieve this using Avalanche gain the intrinsic noise of Avalanche Multiplication must be reduced. Theoretical calculations and experiments examining the noise properties of an imaging system implementing Avalanche Multiplication in a layer of a‐Se are presented. The results indicated that Avalanche Multiplication in a‐Se can have the potential to improve the performance of flat‐panel detectors in fluoroscopy.
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Experimentally validated theoretical model of Avalanche Multiplication x-ray noise in amorphous selenium
Medical Imaging 2000: Physics of Medical Imaging, 2000Co-Authors: Dylan C. Hunt, Brian Lui, John A. RowlandsAbstract:We are investigating active matrix flat panel x-ray detectors for real-time operation in the fluoroscopic exposure range. The typical exposure range for fluoroscopy is low, (0.1 - 10 (mu) R/frame). Hence the flat panel must be very sensitive to produce quantum noise limited images. The application of Avalanche Multiplication in amorphus selenium, ((alpha) -Se) is examined. Avalanche Multiplication, M, can be used to increase signal size, potentially eliminating the quantum sink at low exposure levels. However, M greater than 1 also causes an overall degradation of DQE due to the addition of a new source of gain fluctuation noise. Using a linear cascaded systems model, this noise can be expressed as an additional Avalanche Swank factor A (alpha ) in the expression for DQE(0) equals (eta) A s A (alpha ) where (eta) is the quantum efficiency, A S is the conventional conversion gain Swank factor. Depending upon the parameters, the value of A (alpha ) can vary from unity to less than 0.2. Our model was in agreement with experimentally observed values of A (alpha ) obtained using an imaging system (HARP) with (alpha) -Se layers capable of Avalanche Multiplication. The results indicate that a balance must be maintained between the improvement from Avalanche Multiplication to the amplifier noise limited part of the image, and the degradation effect it has on the quantum noise limited parts of the image. It also suggests that proper engineering of the Avalanche layer can minimize, and perhaps eliminate, the additional noise fluctuations arising from Avalanche Multiplication of x-ray signals.
Kenkichi Tanioka - One of the best experts on this subject based on the ideXlab platform.
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Avalanche Multiplication and impact ionization in amorphous selenium photoconductive target
Japanese Journal of Applied Physics, 2014Co-Authors: Wug-dong Park, Kenkichi TaniokaAbstract:The Avalanche Multiplication factor and the hole ionization coefficient in the amorphous selenium (a-Se) high-gain Avalanche rushing amorphous photoconductor (HARP) target depend on the electric field. The phenomenon of Avalanche Multiplication and impact ionization in the 0.4-µm-thick a-Se HARP target is investigated. The hot carrier energy in the 0.4-µm-thick a-Se HARP target increases linearly as the target voltage increases. The energy relaxation length of hot carriers in the a-Se photoconductor of the 0.4-µm-thick HARP target saturates as the electric field increases. The average energy Eav of a hot carrier and the energy relaxation length λE in the a-Se photoconductor of the 0.4-µm-thick HARP target at 1 × 108 V/m were 0.25 eV and 2.5 nm, respectively. In addition, the hole ionization coefficient β and the Avalanche Multiplication factor M are derived as a function of the electric field, the average energy of a hot carrier, and the impact ionization energy. The experimental hole ionization coefficient β and the Avalanche Multiplication factor M in the 0.4-µm-thick a-Se HARP target agree with the theoretical results.
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Heat treatment to prevent image defect occurrence in amorphous Se doped with Te Avalanche Multiplication photoconductive film
physica status solidi (c), 2011Co-Authors: Y. Ohkawa, Kenkichi Tanioka, Misao Kubota, Kazunori Miyakawa, Tomoki Matsubara, Kenji Kikuchi, Norifumi Egami, Akira KobayashiAbstract:We have been developing an amorphous selenium (a-Se) Avalanche Multiplication photoconductive film, named HARP (high-gain Avalanche rushing amorphous photoconductor), for the purpose of making a high-sensitivity video camera useful for broadcasting, x-ray medical diagnosis, etc. The HARP film used for the red channel in a colour camera is doped with tellurium (Te) to improve its red-light sensitivity. However, doping a-Se with Te generates impurity levels that trap electrons, and the built-in-field formed by these trapped electrons causes image defects. We devised a heat treatment to prevent the occurrence of these defects. We suppose that the thermal energy of the heat treatment releases the originally trapped electrons, and that the energy makes it difficult for moving electrons to be trapped during operation. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Avalanche Multiplication in amorphous selenium and its utilization in imaging
Journal of Non-crystalline Solids, 2008Co-Authors: A. Reznik, Kenkichi Tanioka, Oleg Rubel, Safa Kasap, Y. Ohkawa, S. D. Baranovskii, K. Jandieri, Misao Kubota, John A. RowlandsAbstract:Abstract Amorphous selenium (a-Se) is a well known photoconductor that is currently used in X-ray image detectors and HARP video tubes. Recent advances have made it practical to operate a-Se at extremely high electric fields F , where Avalanche Multiplication occurs. At sufficiently high fields, the effective quantum efficiency ( η ∗ ) (or the overall yield) of the photoconductor can be increased several orders of magnitude above unity and renders Avalanche a-Se photoconductors a prospective alternative to vacuum photomultiplier tubes (PMTs) and silicon Avalanche photodiodes (APDs). In this work we report our study of η ∗ and charge transport for a-Se Avalanche photoconductors with different photoconductive layer thicknesses in wide range of F . Our study shows that a-Se is able to produce a gain of ∼1000 with a rise time of ∼1 ns, both of which clearly point to the potential (or realized) use of this photoconductor in a variety of imaging applications. Furthermore, our work supports the validity of the so-called modified Lucky drift model to explain the nature of impact ionization and Avalanche in this material.
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X‐ray imaging using Avalanche Multiplication in amorphous selenium: Investigation of intrinsic Avalanche noise
Medical physics, 2007Co-Authors: Dylan C. Hunt, Kenkichi Tanioka, John A. RowlandsAbstract:The flat-panel detector (FPD) is the state-of-the-art detector for digital radiography. The FPD can acquire images in real-time, has superior spatial resolution, and is free of the problems of x-ray image intensifiers-veiling glare, pin-cushion and magnetic distortion. However, FPDs suffer from poor signal to noise ratio performance at typical fluoroscopic exposure rates where the quantum noise is reduced to the point that it becomes comparable to the fixed electronic noise. It has been shown previously that Avalanche Multiplication gain in amorphous selenium (a-Se) can provide the necessary amplification to overcome the electronic noise of the FPD. Avalanche Multiplication, however, comes with its own intrinsic contribution to the noise in the form of gain fluctuation noise. In this article a cascaded systems analysis is used to present a modified metric related to the detective quantum efficiency. The modified metric is used to study a diagnostic x-ray imaging system in the presence of intrinsic Avalanche Multiplication noise independently from other noise sources, such as electronic noise. An indirect conversion imaging system is considered to make the study independent of other Avalanche Multiplication related noise sources, such as the fluctuations arising from the depth of x-ray absorption. In this case all the Avalanche events are initiated at the surface of the Avalanche layer, and there are no fluctuations in the depth of absorption. Experiments on an indirect conversion x-ray imaging system using Avalanche Multiplication in a layer of a-Se are also presented. The cascaded systems analysis shows that intrinsic noise of Avalanche Multiplication will not have any deleterious influence on detector performance at zero spatial frequency in x-ray imaging provided the product of conversion gain, coupling efficiency, and optical quantum efficiency are much greater than a factor of 2. The experimental results show that Avalanche Multiplication in a-Se behaves as an intrinsic noise free Avalanche Multiplication, in accordance with our theory. Provided good coupling efficiency and high optical quantum efficiency are maintained, Avalanche Multiplication in a-Se has the potential to increase the gain and make negligible contribution to the noise, thereby improving the performance of indirect FPDs in fluoroscopy.
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Avalanche Multiplication phenomenon in amorphous semiconductors amorphous selenium versus hydrogenated amorphous silicon
Journal of Applied Physics, 2007Co-Authors: A Reznik, Kenkichi Tanioka, Y. Ohkawa, S. D. Baranovskii, O Rubel, Gytis Juska, S O Kasap, J. A. RowlandsAbstract:Although the effect of the impact ionization and the consequent Avalanche Multiplication in amorphous selenium (a-Se) was established long ago and has led to the development and commercialization of ultrasensitive video tubes, the underlying physics of these phenomena in amorphous semiconductors has not yet been fully understood. In particular, it is puzzling why this effect has been evidenced at practical electric fields only in a-Se among all amorphous materials. For instance, impact ionization seems much more feasible in hydrogenated amorphous silicon (a-Si:H) since the charge carrier mobility in a-Si:H is much higher than that in a-Se and also the amount of energy needed for ionization of secondary carriers in a-Si:H is lower than that in a-Se. Using the description of the Avalanche effect based on the lucky-drift model recently developed for amorphous semiconductors we show how this intriguing question can be answered. It is the higher phonon energy in a-Si:H than that in a-Se, which is responsible f...
Chee Hing Tan - One of the best experts on this subject based on the ideXlab platform.
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Avalanche Multiplication and Excess Noise in InAs Electron Avalanche Photodiodes at 77 K
IEEE Journal of Quantum Electronics, 2011Co-Authors: Andrew R. J. Marshall, Pin Jern Ker, John P. R. David, Peter Vines, Chee Hing TanAbstract:The findings of a study of impact ionization, Avalanche Multiplication and excess noise in InAs Avalanche photodiodes at 77 K are reported. It is shown that hole impact ionization is negligible in practical devices which continue to operate as electron Avalanche photodiodes, as they do at room temperature. A new electron ionization coefficient capable of modeling Multiplication at 77 K is presented and it is shown that significant Multiplication can be achieved in practical devices without excessive tunneling currents. The characteristic changes observed between room temperature and 77 K are discussed. This paper helps to demonstrate the potential for practical InAs electron Avalanche photodiodes, operating cooled.
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Temperature dependence of the Avalanche Multiplication process and the impact ionization coefficients in Al0.8Ga0.2As
Nuclear Instruments and Methods in Physics Research Section A: Accelerators Spectrometers Detectors and Associated Equipment, 2011Co-Authors: A.m. Barnett, Chee Hing Tan, J.e. Lees, D.j. Bassford, R.b. GomesAbstract:Abstract The temperature dependence of the Avalanche Multiplication process at soft X-ray energies in Al 0.8 Ga 0.2 As Avalanche photodiodes (APDs) is investigated at temperatures from +80 to −20 °C. The temperature dependence of the pure electron initiated Multiplication factor ( M e ) and the mixed carrier initiated Avalanche Multiplication factor ( M mix ) is experimentally measured. The experimental results are compared with a spectroscopic Monte Carlo model for Al 0.8 Ga 0.2 As diodes from which the temperature dependence of the pure hole initiated Multiplication factor ( M h ) is determined. The temperature dependences of the electron and hole ionization coefficients in Al 0.8 Ga 0.2 As are reported for the first time.
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Modeling of Avalanche Multiplication and excess noise factor in In0.52Al0.48As Avalanche photodiodes using a simple Monte Carlo model
Journal of Applied Physics, 2008Co-Authors: S. C. Liew Tat Mun, Andrew R. J. Marshall, Chee Hing Tan, Y. L. Goh, John P. R. DavidAbstract:A simple Monte Carlo model has been developed to simulate the Avalanche Multiplication process in In0.52Al0.48As. The model reproduces Avalanche Multiplication and excess noise factor measured on a wide range of In0.52Al0.48As p+-n-n+, n+-n-p+, and p+-n+ diodes and confirms that very low excess noise factor can be obtained using pure electron injection in very thick diodes with Avalanche region greater than 2.21 μm or in very thin diodes with Avalanche region lesser than 0.11 μm. In addition we investigated the effect of an electric field gradient in the Avalanche region of Avalanche photodiodes and found that the excess noise factor can be reduced with electric field gradients. However in thin diodes with Avalanche region lesser than 0.20 μm, the onset of tunneling current negates the excess noise reduction achieved using the electric field gradient. Therefore ideal p+-i-n+ diodes still provide the overall preferred structure.
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Avalanche Multiplication in InAlAs
IEEE Transactions on Electron Devices, 2007Co-Authors: Y. L. Goh, Andrew R. J. Marshall, John P. R. David, Chee Hing Tan, G J Rees, D.j. Massey, Mark Hopkinson, S.k. JonesAbstract:A systematic study of Avalanche Multiplication on a series of In 0.52Al0.48As p+-i-n+ and n +-i-p+ diodes with nominal intrinsic region thicknesses ranging from 0.1 to 2.5 mum has been used to deduce effective ionization coefficients between 220 and 980 kVmiddotcm-1. The electron and hole ionization coefficient ratio varies from 32.6 to 1.2 with increasing field. Tunneling begins to dominate the bulk current prior to Avalanche breakdown in the 0.1-mum-thick structure, imposing an upper limit to the operating field. While the local model can accurately predict the breakdown in the diodes, Multiplication is overestimated at low fields. The effects of ionization dead space, which becomes more significant as the intrinsic region thickness reduces, can be corrected for by using a simple correction technique
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Effect of Dead Space on Low-Field Avalanche Multiplication in InP
IEEE Transactions on Electron Devices, 2007Co-Authors: L.j.j. Tan, Mark Hopkinson, Chee Hing Tan, John P. R. DavidAbstract:A systematic study of Avalanche Multiplication behavior in InP has been performed on a series of diodes with Avalanche region widths w ranging from 2.50 to 0.08 mum. The local model for impact ionization is found to increasingly overestimate the Multiplication at low electric fields as w decreases due to the presence of dead space. The suppression of the Multiplication can be modeled accurately by applying a simple correction for the injected carrier dead space to the local model, which enables the Multiplication to be accurately predicted over a wide range of Avalanche region widths.