Experimental performances and Monte Carlo modelling of LWIR HgCdTe avalanche photodiodes

Derelle, Sophie; Bernhardt, Sylvie; Haïdar, Riad; Deschamps, Joël; Primot, Jérôme; Rothman, J.; Rommeluère, Sylvain; Guérineau, Nicolas

doi:10.1117/12.821185

Cited by 7 publications

(10 citation statements)

References 3 publications

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“…16 and 17, and a more detailed study of the dependence of transit time on gain and junction width will be published elsewhere. 18 The qualitative agreement with the estimated electron velocity in Fig. 12 shows that the observed saturation and reduction of the electron velocity is consistent with the combined effect of the nonparabolic conduction band (which limits the speed of the electrons to v e = 2 9 10 8 cm/s at high energies 15 ) and the scattering mechanisms included in the simulations, i.e., phonon scattering, alloy scattering, and impact ionization.…”

Section: Transit-time Estimationssupporting

confidence: 77%

Study of the Transit-Time Limitations of the Impulse Response in Mid-Wave Infrared HgCdTe Avalanche Photodiodes

Perrais

Derelle

Mollard

et al. 2009

Journal of Elec Materi

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The impulse response in frontside-illuminated mid-wave infrared HgCdTe electron avalanche photodiodes (APDs) has been measured with localized photoexcitation at varying positions in the depletion layer. Gain measurements have shown an exponential gain, with a maximum value of M = 5000 for the diffusion current at a reverse bias of V b = 12 V. When the light was injected in the depletion layer, the gain was reduced as the injection approached the N+ edge of the junction. The impulse response was limited by the diode series resistance-capacitance product, RC, due to the large capacitance of the diode metallization. Hence, the fall time is given by the RC constant, estimated as RC = 270 ps, and the rise time is due to the charging of the diode capacitance via the transit and multiplication of carriers in the depletion layer. The latter varies between t 10-90 = 20 ps (at intermediate gains M < 500) and t 10-90 = 70 ps (at M = 3500). The corresponding RC-limited bandwidth is BW = 600 MHz, which yields a new absolute record in gainbandwidth product of GBW = 2.1 THz. The increase in rise time at high gains indicates the existence of a limit in the transit-time-limited gain-bandwidth product, GBW = 19 THz. The impulse response was modeled using a onedimensional deterministic model, which allowed a quantitative analysis of the data in terms of the average velocity of electrons and holes. The fitting of the data yielded a saturation of the electron and hole velocity of v e = 2.3 9 10 7 cm/s and v h = 1.0 9 10 7 cm/s at electric fields E > 1.5 kV/cm. The increase in rise time at high bias is consistent with the results of Monte Carlo simulations and can be partly explained by a reduction of the electron saturation velocity due to frequent impact ionization. Finally, the model was used to predict the bandwidth in diodes with shorter RC = 5 ps, giving BW = 16 GHz and BW = 21 GHz for x j = 4 lm and x j = 2 lm, respectively, for a gain of M = 100.

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Section: Transit-time Estimationssupporting

confidence: 77%

Study of the Transit-Time Limitations of the Impulse Response in Mid-Wave Infrared HgCdTe Avalanche Photodiodes

Perrais

Derelle

Mollard

et al. 2009

Journal of Elec Materi

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“…are also expected in HgCdTe e-APDs [19], [20], although these differ slightly from the trend identified here for InAs e-APDs.…”

Section: A Photomultiplication Characteristicscontrasting

confidence: 36%

Impact Ionization in InAs Electron Avalanche Photodiodes

Marshall

David

Tan

2010

IEEE Trans. Electron Devices

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Abstract-A systematic study of impact ionization, avalanche multiplication, and excess noise in InAs diodes has been carried out, confirming that avalanche multiplication is dominated by the impact ionization of electrons. This results in highly desirable "electron avalanche photodiode" characteristics previously only demonstrated in HgCdTe diodes, which are discussed in detail. The suppression of excess noise by nonlocal effects, to levels below the local model minimum of F = 2, is explained. An electron ionization coefficient is calculated and shown to be capable of modeling the electron impact ionization, which differs characteristically from that in wider bandgap III-V materials.Index Terms-Avalanche photodiode (APD), electron avalanche photodiode (e-APD), impact ionization, InAs, ionization coefficient.

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“…5 Figure 4 presents the calculated electron and hole steady-state drift velocity of Hg 0.7 Cd 0.3 Te at 80 K. The peak electron drift velocity is estimated at 2.1 9 10 7 cm/s for an applied field strength of 2 kV/cm. The negative differential mobility was found to be due to the strong nonparabolicity of the conduction band rather than to electron transfer to secondary valleys.…”

Section: Resultsmentioning

confidence: 99%

“…The ''Results'' section presents the calculated gain and noise figures of HgCdTe MWIR and LWIR APDs fabricated by CEA/LETI and provides comparison with available experimental data. 5 Finally, ''Conclusions'' are presented.…”

Section: Introductionmentioning

confidence: 99%

“…1 Several groups have reported an exponential gain curve and extremely low multiplication noise in electroninjected HgCdTe avalanche photodetectors (APDs) at temperatures in the range of 77 K to 260 K for a variety of cutoff wavelengths in the MWIR and LWIR bands. [2][3][4][5] These exceptional characteristics of HgCdTe APDs are indicative of the exclusive impact ionization of the electrons and of dead-space effects that tend to introduce order in the random impact ionization process, i.e., a history-dependent gain mechanism. 6,7 The electron impact ionization process in HgCdTe becomes important at relatively small electric fields due to the high mobility of electrons and their low impact ionization threshold energy.…”

Section: Introductionmentioning

confidence: 99%

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Full-Band Monte Carlo Simulation of HgCdTe APDs

Bertazzi

Moresco

Penna

et al. 2010

Journal of Elec Materi

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A full-band Monte Carlo model has been developed for understanding the carrier multiplication process in HgCdTe infrared avalanche photodiodes. The proposed model is based on a realistic electronic structure obtained by pseudopotential calculations and a phonon dispersion relation determined by ab initio techniques. The calculated carrier-phonon scattering rates are consistent with the electronic structure and the phonon dispersion relation, thus removing adjustable parameters such as deformation potential coefficients. The computation of the impact ionization transition rate is based on the calculated electronic structure and the corresponding wavevector-dependent dielectric function. The Monte Carlo model is applied to investigate key performance figures of long-wavelength infrared (LWIR) and mid-wavelength infrared (MWIR) HgCdTe avalanche photodetectors such as carrier multiplication and noise properties. Good agreement is achieved between simulations and experimental results. The multiplication process in LWIR (k c = 9.0 lm at 80 K) and MWIR (k c = 5.1 lm at 80 K) devices is found to be initiated only by electrons, as expected from excess noise measurements. This single-carrier multiplication behavior can be traced back to the details of the computed valence-band structure and phonon scattering rates.

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Experimental performances and Monte Carlo modelling of LWIR HgCdTe avalanche photodiodes

Cited by 7 publications

References 3 publications

Study of the Transit-Time Limitations of the Impulse Response in Mid-Wave Infrared HgCdTe Avalanche Photodiodes

Study of the Transit-Time Limitations of the Impulse Response in Mid-Wave Infrared HgCdTe Avalanche Photodiodes

Impact Ionization in InAs Electron Avalanche Photodiodes

Full-Band Monte Carlo Simulation of HgCdTe APDs

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