Gain and Dark Current Characteristics of Planar HgCdTe Avalanche Photo Diodes

Abstract

HgCdTe midwave infrared pin avalanche photodiodes (APDs) have been studied as a function of temperature and bias, for two types of junction profiles with different nominal junction width and the same cut-off wavelength kc = 5.0 lm at T = 77 K. A gain of 5,300 at a reverse bias of 12.5 V was demonstrated in the nominally wide junction pin-APD at T = 77 K. The nominally narrow pin-APD showed a higher gain at low bias, but the maximum gain was lower due to an earlier onset of excess currents. The gain was measured for temperatures (T) between 30 K and 150 K and was found to decrease with increasing temperatures, in correlation with the increase in band gap. However, the useful gain was reduced at lower temperatures, due to increased excess current at high reverse bias, indicating a tunnel limited origin of the sensitivity limiting excess current. The noise factor, F, showed a nearly deterministic multiplication of the carriers, with F = 1-1.5 up to gains of 5,000.

HgCdTe detectors for space and science imaging in France: general issues and latest achievements

“…Indeed, the possibility to pre-amplify the incoming photonic signal into the photodiode itself (with no major degradation of the signal to noise ratio [ 11 ]) is very interesting when the detection performance is limited by the ROIC noise as it is the case in the very low flux detection for astronomy. The APD data reported in Figure 1 has been measured on a 30µm pitch 320x526 focal plane array with 3µm cutoff.…”

Infrared Avalanche Photodiode Detectors

“…A variety of environmental, electrical, and radiometric parameters should be taken into account and carefully controlled. Dark current and the excess noise should be minimised to achieve better performance of APD's [43][44] . High performance of HgCdTe APD has been demonstrated due to the development of advanced device structures and materials.…”

“…The doping concentration of υ-region is required to low (< 5 × 10 14 cm -3 ) for avoiding the tunneling current contribution at higher bias. If dark current contribution appears into the photocurrent, we can no longer differentiate the avalanche phenomena from the tunneling one [42][43][44] . Low generation recombination current is also seen in the low bias regime in the APD.…”

“…Hence, larger gain at low bias is obtained in narrow devices, which can be advantageous if the APD can be used with Readout integrated circuits (ROIC) in which the maximum bias can be limited. But, the tunneling current might be contributed in those APD having narrow depletion region [43][44] . Therefore, optimisation of depletion width is very crucial in MWIR e-APD.…”

“…Therefore, gain is determined from the I-V measurements under illumination condition. The avalanche gain M is calculated by normalizing the photo current for MWIR APD at 80 K and is given as 4,44 .…”