Modeling and analysis of photoconductive detectors based on Hg1-x Cd x Te for free space optical communication

Abstract

In this paper we report a theoretical analysis of a long wavelength photoconductive detector for characterizing and optimizing the device in respect of voltage responsivity, quantum efficiency, detectivity and noise equivalent power. The model has been applied to examine the potential of an n-type Hg 0.77 Cd 0.23 Te photoconductive detector for possible application in free space optical communication system operating at the atmospheric window near 9.6 µ m. In the present analysis we have taken into account all the major recombination mechanisms (e.g., Radiative, Auger, and Shockley-Read-Hall types) including the effect of surface recombination at the interfaces that shape the characteristics of photoconductor. The results obtained on the basis of our analysis reveal that in the absence of surface recombination the device exhibits a peak quantum efficiency of 90%, a maximum detectivity of 10 8 MHz 1/2 /W at 77 K, a 3 dB bandwidth of 117.86 MHz and noise voltage of 5.4 × 10 −6 V/Hz 1/2 . The sweep-out effect has been found to degrade the detectivity nearly by a factor of 10 at the same temperature and wavelength of operation. The estimated noise equivalent power of the photodetector is of the order of 10 −9 W at 9.6 µm wavelength.

Bilayer graphene/HgCdTe based very long infrared photodetector with superior external quantum efficiency, responsivity, and detectivity

“…The doping and carrier densities are evaluated using Fermi-Dirac statistics. 15,24,78 The performance of the photodetector at 77 K is evaluated analytically for the operation at the wavelength of 20.6 mm. The photons having energy greater than the bandgap create electron-hole pairs in the lightly doped n-region.…”

Sensitivity analysis of an HgCdTe based photovoltaic receiver for long-wavelength free space optical communication systems

“…Since the noise is dominated by the thermal noise sources in the preamplifier, it is necessary to reduce the noise of the preamplifier in p-i-n/FET or p-i-n/HBT photoreceivers to improve the sensitivity of the overall receiver. Recently HgCdTe based photoconductive detectors have been proposed for free space optical communication [6] . These detectors have bandwidth limitation.…”