Performance and Modeling of the MWIR HgCdTe Electron Avalanche Photodiode

Abstract

The operation of the mid-wave infrared (MWIR) HgCdTe cylindrical electron injection avalanche photodiode (e-APD) is described. The measured gain and excess noise factor are related to the collection region fill factor. A twodimensional diffusion model calculates the time-dependent response and steady-state pixel point spread function for cylindrical diodes, and predicts bandwidths near 1 GHz for small geometries. A 2 lm diameter spot scan system was developed for point spread function and crosstalk measurements at 80 K. An electron diffusion length of 13.4 lm was extracted from spot scan data. Bandwidth data are shown that indicate bandwidths in excess of 300 MHz for small unit cells geometries. Dark current data, at high gain levels, indicate an effective gain normalized dark density count as low as 1000 counts/ls/cm 2 at an APD gain of 444. A junction doping profile was determined from capacitance-voltage data. Spectral response data shows a gain-independent characteristic.

Infrared Avalanche Photodiode Detectors

“…The multiplication process is started at low reverse bias. The resultant gain increases exponentially with the reverse bias in our fabricated APD device 49,53 .…”

“…Finally, it is concluded that electron-injection multiplication process is more favorable from SWIR to LWIR APD for achieving high gain at low reverse bias with low noise. Beck 49,61 , et al have developed MWIR HgCdTe cylindrical p-around-n e-APD with gain~ 1000 and very low gain normalised dark current density (< 0.7 nA/cm 2 ). However, they reported that the planar APD structure provides fill factor~ 100 % and the collection efficiency > 90%, whereas HDVIP diode has advantage to yields low dark current, high quantum efficiency and high operability.…”

“…HgCdTe APD is an attractive choice for many IR applications such as LIDAR/ LADAR, defence, night vision, optical communications & atmospheric studies [9][10][11][45][46] . HgCdTe based SWIR APDs can be used as sensor in the LADAR system or 3-D imaging applications 40,[47][48][49][50][51][52][53][54][55][56][57][58][59][60] . CEA-LETI has been involved in the development of HgCdTe based e-APD focal plane array for Passive (thermal imaging) and active (2D/3D flash LADAR imaging) imaging since last a few years.…”

Comparison of flash lidar detector options

“…Because this dark current is generated in the multiplication region, it is likely not to be fully gained, and, indeed, noise measurements indicate this. 23 A simplified manner of handling the dark current in the modeling is to use measured dark currents at the bias that achieve the required APD gain. This dark current is then divided by the gain to give a gain normalized dark current.…”

HgCdTe e-avalanche photodiode detector arrays

“…High gain with ultra low excess noise factor has been reported in MWIR HgCdTe e-APDs by several groups. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Results on design, fabrication and characterization of e-APD detector arrays using LPE grown p-HgCdTe epilayers are presented in this paper. Consideration of active cum passive modes of operation has been kept in mind in the development of these detector arrays.…”