stephen plimmer - Academia.edu (original) (raw)
Papers by stephen plimmer
Non-equilibrium modelling of avalanche photodiode speed
The 15th Annual Meeting of the IEEE Lasers and Electro-Optics Society
Avalanche photodiodes (APDs) are particularly suited to detecting weak optical signals. However, ... more Avalanche photodiodes (APDs) are particularly suited to detecting weak optical signals. However, in general, they suffer from a bandwidth limitation imposed by carrier feedback within the avalanche process. Although faster response times can be obtained by reducing the length of the avalanche region, dead space increasingly degrades the improvement relative to predictions from a purely local ionization model using the same velocities for the carriers. Conventionally these velocities are chosen to be the carriers' saturated drift velocities, vs. However, our recent Monte Carlo (MC) modelling showed that an enhancement in the mean velocities of carriers to ionization in short (<0.3 μm) APDs produces a much faster avalanche speed than a model with similar spatial ionization using saturated drift velocities. This velocity enhancement promises to compensate for the dead space degradation although the extent is not clear. For example, if the velocity enhancement overcompensates, APD bandwidth will be greater than expected from a local ionization model using vs. Since the latter (conventional) model is particularly popular for APD bandwidth a study of its accuracy in a non-equilibrium regime is desirable. The results obtained suggest that APDs with short avalanche regions can be expected to operate more quickly than conventional model predictions, particularly so in very short devices.
Impact ionization in Al Ga As-GaAs single heterostruc-tures
Improved excess noise and temperature dependence of multiplication characteristics in thin InP avalanching regions
Conference Proceedings. Eleventh International Conference on Indium Phosphide and Related Materials (IPRM'99) (Cat. No.99CH36362)
ABSTRACT
Avalanche multiplication noise in bulk and thin AI(x)Ga(1-x)As (x=0-0.8) PIN and NIP diodes
Proceedings of SPIE - The International Society for Optical Engineering
The avalanche multiplication noise characteristics of AlxGa1-xAs (x equals 0-0.8) have been measu... more The avalanche multiplication noise characteristics of AlxGa1-xAs (x equals 0-0.8) have been measured in a wide range of PIN and NIP diodes. The study includes determining the effect of the alloy fraction, x, as it varies from 0 to 0.8 while the effect of the avalanche width, w, is investigated by varying it from 1 micrometers down to 0.05 micrometers . For x equals 0-0.6, the ratio of the electron to hole ionization coefficients, 1/k, decreases from 3 (for x equals 0) to 1 (for x equals 0.6), leading to higher noise in a local prediction as x increases. Measurements for x equals 0-0.6 in nominally 1um thick diodes indicates that the excess noise factor can be approximately predicted by the local model. However, as the avalanche width reduces, a lower than expected noise factor was measured. This behaviour is associated with the effect of deadspace, whereby carriers have insufficient energy to initiate ionization for a significant region of the device. The presence of deadspace leads...
How avalanche pulses evolve in space and time
How avalanche pulses evolve in space and time. [Proceedings of SPIE 4283, 511 (2001)]. SA Plimmer... more How avalanche pulses evolve in space and time. [Proceedings of SPIE 4283, 511 (2001)]. SA Plimmer, Paul J. Hambleton, Beng K. Ng, GM Dunn, Jo S. Ng, John PR David, Graham J. Rees. Abstract. Conventional models of the ...
Limitations of the saturated drift velocity approximation for time domain modelling
Semiconductor Science and Technology, 2002
The time response of APDs is conventionally modelled assuming that carriers travel always at thei... more The time response of APDs is conventionally modelled assuming that carriers travel always at their saturated drift velocity. The present study tests this assumption by comparing the distributions of carrier exit times in an avalanche process predicted from this conventional model and from a Monte Carlo model incorporating more realistic transport behaviour. While the two treatments give very similar results in a long (1.0 μm) structure, as the device width is reduced, the results from the conventional model increasingly diverge from those of the Monte Carlo model, with the latter predicting faster avalanche processes, so that in a 0.1 μm thick structure the speed predictions differ by more than a factor of 3. These results confirm that non-equilibrium transport plays an important part in the time response of sub-micron devices, where the conventional modelling approach is inappropriate.
Simulated current response in avalanche photodiodes
Journal of Applied Physics, 2002
[Journal of Applied Physics 91, 2107 (2002)]. PJ Hambleton, SA Plimmer, JPR David, GJ Rees, GM Du... more [Journal of Applied Physics 91, 2107 (2002)]. PJ Hambleton, SA Plimmer, JPR David, GJ Rees, GM Dunn. Abstract. The time dependent current response to an impulse of injected carriers is calculated for an avalanche photodiode using Monte Carlo simulation. ...
Impact ionization in thin AlxGa1−xAs (x=0.15 and 0.30)p-i-ndiodes
Journal of Applied Physics, 1997
The electron and hole multiplication characteristics, Me and Mh, respectively, have been measured... more The electron and hole multiplication characteristics, Me and Mh, respectively, have been measured in two series of AlxGa1−xAs(x=0.15 and 0.30) p-i-n diodes where the i-region thicknesses, w, vary from 1.0 down to 0.025 μm. From these, the effective electron and hole ionization coefficients, α and β, respectively, have been determined and in the thicker structures agreement is found with data
![Research paper thumbnail of Avalanche noise characteristics of thin GaAs structures with distributed carrier generation [APDs]](https://attachments.academia-assets.com/94921056/thumbnails/1.jpg)
](IEEE Transactions on Electron Devices, 2000
(5 more authors) (2000) Avalanche noise characteristics of thin GaAs structures with distributed ... more (5 more authors) (2000) Avalanche noise characteristics of thin GaAs structures with distributed carrier generation. IEEE Transactions on Electron Devices, 47 (5). pp. 910-914.
IEEE Transactions on Electron Devices, 1996
The electron and hole multiplication coefficients, Me and lwh, respectively, have been measured i... more The electron and hole multiplication coefficients, Me and lwh, respectively, have been measured in thin GaAs homojunction PIN and NIP diodes and from conventional ionization analysis the effective electron and hole ionization coefficients, a and /?, respectively, have been determined. The nominal intrinsic region thickness (U of these structures ranges from 1.0 bcm down to 25 nm. In the thicker structures, bulk-like behavior is observed; however, in the thinner structures, significant differences are found. As the i-regions become thinner and the electric fields increase, the M c / M h ratio is seen to approach unity. The experimental results are modeled and interpreted using a semianalytical solution of the Boltzmann equation. In thin (w < 0.1 pm) devices the dead space effect reduces effective ionization coefficients below their bulk values at low values of carrier multiplication. However, overshoot effects compensate for this at extremely high fields (21 x lo3 kV/cm).
Spatial limitations to the application of the lucky-drift theory of impact ionization
IEEE Transactions on Electron Devices, 1997
Multiplication characteristics predicted by the lucky-drift (LD) theory of impact ionization are ... more Multiplication characteristics predicted by the lucky-drift (LD) theory of impact ionization are compared to experimental results on a range of thin GaAs PIN diodes with i-region thicknesses, w, from 1 μm down to 0.025 μm. Whereas lucky-drift and experimental results are in agreement for w&amp;amp;amp;amp;amp;ges;0.1 μm, significant differences are observed for thinner structures where nonlocal effects are important. Multiplication characteristics
IEEE Transactions on Electron Devices, 2003
The nonlocal enhancement in the velocities of charge carriers to ionization is shown to outweigh ... more The nonlocal enhancement in the velocities of charge carriers to ionization is shown to outweigh the opposing effects of dead space, increasing the avalanche speed of short avalanche photodiodes (APDs) over the predictions of a conventional local model which ignores both of these effects. The trends in the measured gain-bandwidth product of two short InAlAs APDs reported in the literature support this result. Relatively large speed benefits are predicted to result from further small reductions in the lengths of short multiplication regions.
IEEE Transactions on Electron Devices, 2001
Avalanche multiplication and excess noise were measured on a series of Al 0 6 Ga 0 4 As p + in + ... more Avalanche multiplication and excess noise were measured on a series of Al 0 6 Ga 0 4 As p + in + and n + ip + diodes, with avalanche region thickness, ranging from 0.026 m to 0.85 m. The results show that the ionization coefficient for electrons is slightly higher than for holes in thick, bulk material. At fixed multiplication values the excess noise factor was found to decrease with decreasing , irrespective of injected carrier type. Owing to the wide Al 0 6 Ga 0 4 As bandgap extremely thin devices can sustain very high electric fields, giving rise to very low excess noise factors, of around 3.3 at a multiplication factor of 15.5 in the structure with = 0.026 m. This is the lowest reported excess noise at this value of multiplication for devices grown on GaAs substrates. Recursion equation modeling, using both a hard threshold dead space model and one which incorporates the detailed history of the ionizing carriers, is used to model the nonlocal nature of impact ionization giving rise to the reduction in excess noise with decreasing. Although the hard threshold dead space model could reproduce qualitatively the experimental results better agreement was obtained from the history-dependent model. Index Terms-Al Ga 1 As, avalanche photodiodes, excess noise, impact ionization.
IEEE Transactions on Electron Devices, 1999
A simple Monte Carlo model (SMC) using single effective parabolic valleys and accurately accounti... more A simple Monte Carlo model (SMC) using single effective parabolic valleys and accurately accounting for deadspace effects is presented for calculating the avalanche process. Very good agreement is achieved with a range of measured electron and hole multiplication results from GaAs p +-iN + 's with iregion thicknesses, w, from 1 m down to 0.025 m and with the excess noise factors down to 0.05 m. While the results are insensitive to the precise values of input parameter for structures with w 0:2 m, this is not the case in thinner structures where the deadspace represents a significant fraction of the device. For w < 0:2 m, the energy dependence of the ionization rate becomes increasingly important. The SMC model is tested against a full-band Monte Carlo model (FBMC) by comparing the mean distance between ionization events and the probability density functions, which are effectively the histograms of distances between ionization events, for equivalent material parameters. The good agreement between these suggests that the SMC, with a relatively small number of fitting parameters and much faster calculation times than the FBMC, is a useful tool for device simulation and interpreting experimental results.
IEEE Transactions on Electron Devices, 2000
Electron and hole multiplication characteristics, and have been measured in Al Ga 1 As (=0-0.60) ... more Electron and hole multiplication characteristics, and have been measured in Al Ga 1 As (=0-0.60) homojunction p +-in + diodes with i-region thicknesses, from 1 m to 0.025 m and analyzed using a Monte Carlo model (MC). The effect of the composition on both the macroscopic multiplication characteristics and microscopic behavior is therefore shown for the first time. Increasing the alloy fraction causes the multiplication curves to be shifted to higher voltages such that the multiplication curves at any given thickness are practically parallel for different The ratio also decreases as increases, varying from 2to 1as increases from 0 to 0.60 in a =1 m p +-in + The Monte-Carlo model is also used to extract ionization coefficients and dead-space distances from the measured results which cover electric field ranges from 250 kV/cm-1200 kV/cm in each composition. These parameters can be used to calculate the nonlocal multiplication process by solving recurrence equations. Limitations to the applicability of field-dependent ionization coefficients are shown to arise however when the electric-field profile becomes highly nonuniform.
IEEE Transactions on Electron Devices, 2001
This is a repository copy of Avalanche multiplication characteristics of Al0.8Ga0.2As diodes .
Applied Physics Letters, 2000
The impact ionization coefficients in bulk Al 0.8 Ga 0.2 As have been determined from photomultip... more The impact ionization coefficients in bulk Al 0.8 Ga 0.2 As have been determined from photomultiplication measurements over the electric field range of 328-519 kV/cm. Unlike in Al x Ga 1Ϫx As (xр0.6), where the electron to hole ionization coefficients ratios (1/k) are less than 2, the 1/k value in Al 0.8 Ga 0.2 As was found to be greater than 10. Excess noise measurements corroborated the multiplication results, suggesting that this material may be a suitable multiplication medium for low noise avalanche photodiodes.
![Research paper thumbnail of The merits and limitations of local impact ionization theory [APDs]](https://attachments.academia-assets.com/94921016/thumbnails/1.jpg)
](IEEE Transactions on Electron Devices, 2000
Non-equilibrium modelling of avalanche photodiode speed
The 15th Annual Meeting of the IEEE Lasers and Electro-Optics Society
Avalanche photodiodes (APDs) are particularly suited to detecting weak optical signals. However, ... more Avalanche photodiodes (APDs) are particularly suited to detecting weak optical signals. However, in general, they suffer from a bandwidth limitation imposed by carrier feedback within the avalanche process. Although faster response times can be obtained by reducing the length of the avalanche region, dead space increasingly degrades the improvement relative to predictions from a purely local ionization model using the same velocities for the carriers. Conventionally these velocities are chosen to be the carriers' saturated drift velocities, vs. However, our recent Monte Carlo (MC) modelling showed that an enhancement in the mean velocities of carriers to ionization in short (<0.3 μm) APDs produces a much faster avalanche speed than a model with similar spatial ionization using saturated drift velocities. This velocity enhancement promises to compensate for the dead space degradation although the extent is not clear. For example, if the velocity enhancement overcompensates, APD bandwidth will be greater than expected from a local ionization model using vs. Since the latter (conventional) model is particularly popular for APD bandwidth a study of its accuracy in a non-equilibrium regime is desirable. The results obtained suggest that APDs with short avalanche regions can be expected to operate more quickly than conventional model predictions, particularly so in very short devices.
Impact ionization in Al Ga As-GaAs single heterostruc-tures
Improved excess noise and temperature dependence of multiplication characteristics in thin InP avalanching regions
Conference Proceedings. Eleventh International Conference on Indium Phosphide and Related Materials (IPRM'99) (Cat. No.99CH36362)
ABSTRACT
Avalanche multiplication noise in bulk and thin AI(x)Ga(1-x)As (x=0-0.8) PIN and NIP diodes
Proceedings of SPIE - The International Society for Optical Engineering
The avalanche multiplication noise characteristics of AlxGa1-xAs (x equals 0-0.8) have been measu... more The avalanche multiplication noise characteristics of AlxGa1-xAs (x equals 0-0.8) have been measured in a wide range of PIN and NIP diodes. The study includes determining the effect of the alloy fraction, x, as it varies from 0 to 0.8 while the effect of the avalanche width, w, is investigated by varying it from 1 micrometers down to 0.05 micrometers . For x equals 0-0.6, the ratio of the electron to hole ionization coefficients, 1/k, decreases from 3 (for x equals 0) to 1 (for x equals 0.6), leading to higher noise in a local prediction as x increases. Measurements for x equals 0-0.6 in nominally 1um thick diodes indicates that the excess noise factor can be approximately predicted by the local model. However, as the avalanche width reduces, a lower than expected noise factor was measured. This behaviour is associated with the effect of deadspace, whereby carriers have insufficient energy to initiate ionization for a significant region of the device. The presence of deadspace leads...
How avalanche pulses evolve in space and time
How avalanche pulses evolve in space and time. [Proceedings of SPIE 4283, 511 (2001)]. SA Plimmer... more How avalanche pulses evolve in space and time. [Proceedings of SPIE 4283, 511 (2001)]. SA Plimmer, Paul J. Hambleton, Beng K. Ng, GM Dunn, Jo S. Ng, John PR David, Graham J. Rees. Abstract. Conventional models of the ...
Limitations of the saturated drift velocity approximation for time domain modelling
Semiconductor Science and Technology, 2002
The time response of APDs is conventionally modelled assuming that carriers travel always at thei... more The time response of APDs is conventionally modelled assuming that carriers travel always at their saturated drift velocity. The present study tests this assumption by comparing the distributions of carrier exit times in an avalanche process predicted from this conventional model and from a Monte Carlo model incorporating more realistic transport behaviour. While the two treatments give very similar results in a long (1.0 μm) structure, as the device width is reduced, the results from the conventional model increasingly diverge from those of the Monte Carlo model, with the latter predicting faster avalanche processes, so that in a 0.1 μm thick structure the speed predictions differ by more than a factor of 3. These results confirm that non-equilibrium transport plays an important part in the time response of sub-micron devices, where the conventional modelling approach is inappropriate.
Simulated current response in avalanche photodiodes
Journal of Applied Physics, 2002
[Journal of Applied Physics 91, 2107 (2002)]. PJ Hambleton, SA Plimmer, JPR David, GJ Rees, GM Du... more [Journal of Applied Physics 91, 2107 (2002)]. PJ Hambleton, SA Plimmer, JPR David, GJ Rees, GM Dunn. Abstract. The time dependent current response to an impulse of injected carriers is calculated for an avalanche photodiode using Monte Carlo simulation. ...
Impact ionization in thin AlxGa1−xAs (x=0.15 and 0.30)p-i-ndiodes
Journal of Applied Physics, 1997
The electron and hole multiplication characteristics, Me and Mh, respectively, have been measured... more The electron and hole multiplication characteristics, Me and Mh, respectively, have been measured in two series of AlxGa1−xAs(x=0.15 and 0.30) p-i-n diodes where the i-region thicknesses, w, vary from 1.0 down to 0.025 μm. From these, the effective electron and hole ionization coefficients, α and β, respectively, have been determined and in the thicker structures agreement is found with data
IEEE Transactions on Electron Devices, 2000
(5 more authors) (2000) Avalanche noise characteristics of thin GaAs structures with distributed ... more (5 more authors) (2000) Avalanche noise characteristics of thin GaAs structures with distributed carrier generation. IEEE Transactions on Electron Devices, 47 (5). pp. 910-914.
IEEE Transactions on Electron Devices, 1996
The electron and hole multiplication coefficients, Me and lwh, respectively, have been measured i... more The electron and hole multiplication coefficients, Me and lwh, respectively, have been measured in thin GaAs homojunction PIN and NIP diodes and from conventional ionization analysis the effective electron and hole ionization coefficients, a and /?, respectively, have been determined. The nominal intrinsic region thickness (U of these structures ranges from 1.0 bcm down to 25 nm. In the thicker structures, bulk-like behavior is observed; however, in the thinner structures, significant differences are found. As the i-regions become thinner and the electric fields increase, the M c / M h ratio is seen to approach unity. The experimental results are modeled and interpreted using a semianalytical solution of the Boltzmann equation. In thin (w < 0.1 pm) devices the dead space effect reduces effective ionization coefficients below their bulk values at low values of carrier multiplication. However, overshoot effects compensate for this at extremely high fields (21 x lo3 kV/cm).
Spatial limitations to the application of the lucky-drift theory of impact ionization
IEEE Transactions on Electron Devices, 1997
Multiplication characteristics predicted by the lucky-drift (LD) theory of impact ionization are ... more Multiplication characteristics predicted by the lucky-drift (LD) theory of impact ionization are compared to experimental results on a range of thin GaAs PIN diodes with i-region thicknesses, w, from 1 μm down to 0.025 μm. Whereas lucky-drift and experimental results are in agreement for w&amp;amp;amp;amp;amp;ges;0.1 μm, significant differences are observed for thinner structures where nonlocal effects are important. Multiplication characteristics
IEEE Transactions on Electron Devices, 2003
The nonlocal enhancement in the velocities of charge carriers to ionization is shown to outweigh ... more The nonlocal enhancement in the velocities of charge carriers to ionization is shown to outweigh the opposing effects of dead space, increasing the avalanche speed of short avalanche photodiodes (APDs) over the predictions of a conventional local model which ignores both of these effects. The trends in the measured gain-bandwidth product of two short InAlAs APDs reported in the literature support this result. Relatively large speed benefits are predicted to result from further small reductions in the lengths of short multiplication regions.
IEEE Transactions on Electron Devices, 2001
Avalanche multiplication and excess noise were measured on a series of Al 0 6 Ga 0 4 As p + in + ... more Avalanche multiplication and excess noise were measured on a series of Al 0 6 Ga 0 4 As p + in + and n + ip + diodes, with avalanche region thickness, ranging from 0.026 m to 0.85 m. The results show that the ionization coefficient for electrons is slightly higher than for holes in thick, bulk material. At fixed multiplication values the excess noise factor was found to decrease with decreasing , irrespective of injected carrier type. Owing to the wide Al 0 6 Ga 0 4 As bandgap extremely thin devices can sustain very high electric fields, giving rise to very low excess noise factors, of around 3.3 at a multiplication factor of 15.5 in the structure with = 0.026 m. This is the lowest reported excess noise at this value of multiplication for devices grown on GaAs substrates. Recursion equation modeling, using both a hard threshold dead space model and one which incorporates the detailed history of the ionizing carriers, is used to model the nonlocal nature of impact ionization giving rise to the reduction in excess noise with decreasing. Although the hard threshold dead space model could reproduce qualitatively the experimental results better agreement was obtained from the history-dependent model. Index Terms-Al Ga 1 As, avalanche photodiodes, excess noise, impact ionization.
IEEE Transactions on Electron Devices, 1999
A simple Monte Carlo model (SMC) using single effective parabolic valleys and accurately accounti... more A simple Monte Carlo model (SMC) using single effective parabolic valleys and accurately accounting for deadspace effects is presented for calculating the avalanche process. Very good agreement is achieved with a range of measured electron and hole multiplication results from GaAs p +-iN + 's with iregion thicknesses, w, from 1 m down to 0.025 m and with the excess noise factors down to 0.05 m. While the results are insensitive to the precise values of input parameter for structures with w 0:2 m, this is not the case in thinner structures where the deadspace represents a significant fraction of the device. For w < 0:2 m, the energy dependence of the ionization rate becomes increasingly important. The SMC model is tested against a full-band Monte Carlo model (FBMC) by comparing the mean distance between ionization events and the probability density functions, which are effectively the histograms of distances between ionization events, for equivalent material parameters. The good agreement between these suggests that the SMC, with a relatively small number of fitting parameters and much faster calculation times than the FBMC, is a useful tool for device simulation and interpreting experimental results.
IEEE Transactions on Electron Devices, 2000
Electron and hole multiplication characteristics, and have been measured in Al Ga 1 As (=0-0.60) ... more Electron and hole multiplication characteristics, and have been measured in Al Ga 1 As (=0-0.60) homojunction p +-in + diodes with i-region thicknesses, from 1 m to 0.025 m and analyzed using a Monte Carlo model (MC). The effect of the composition on both the macroscopic multiplication characteristics and microscopic behavior is therefore shown for the first time. Increasing the alloy fraction causes the multiplication curves to be shifted to higher voltages such that the multiplication curves at any given thickness are practically parallel for different The ratio also decreases as increases, varying from 2to 1as increases from 0 to 0.60 in a =1 m p +-in + The Monte-Carlo model is also used to extract ionization coefficients and dead-space distances from the measured results which cover electric field ranges from 250 kV/cm-1200 kV/cm in each composition. These parameters can be used to calculate the nonlocal multiplication process by solving recurrence equations. Limitations to the applicability of field-dependent ionization coefficients are shown to arise however when the electric-field profile becomes highly nonuniform.
IEEE Transactions on Electron Devices, 2001
This is a repository copy of Avalanche multiplication characteristics of Al0.8Ga0.2As diodes .
Applied Physics Letters, 2000
The impact ionization coefficients in bulk Al 0.8 Ga 0.2 As have been determined from photomultip... more The impact ionization coefficients in bulk Al 0.8 Ga 0.2 As have been determined from photomultiplication measurements over the electric field range of 328-519 kV/cm. Unlike in Al x Ga 1Ϫx As (xр0.6), where the electron to hole ionization coefficients ratios (1/k) are less than 2, the 1/k value in Al 0.8 Ga 0.2 As was found to be greater than 10. Excess noise measurements corroborated the multiplication results, suggesting that this material may be a suitable multiplication medium for low noise avalanche photodiodes.
IEEE Transactions on Electron Devices, 2000