(Hg,Cd)Te Photodiode Laser Receivers for the 1-3-micro Spectral Region

Sensitive high speed photodiode detectors have been prepared in various compositions of (Hg,Cd)Te for the 1-micro to 3-micro spectral region. These detectors, operating at room temperature, exhibit quantum efficiencies in the 40-70% range and specific detectivities that range from 3 x 10(11) cm Hz((1/2))/W at 1.3 micro to 5 x 10(9) cm Hz((1/2))/W at 3 micro. Improved performance is possible by cooling the photodiode detector; specific detectivities of 2 x 10(12) cm Hz((1/2))/W approaching the BLIP limit at 2.2 micro have been measured at 77 K. Response time measurements using detector-preamplifier modules have been made with 0.9 <, 1.06 micro, and 1.54-micro, pulsed radiation. The response time of approximately 10 nsec does not appear wavelength-dependent and is limited by the RC product and amplifier bandwidth. When the photodiode is terminated with a very broadband amplifier, the pulse response is limited by the RC product to 0.5 nsec and a secondary time constant of ~5 nsec is observed that is believed to be caused by the transit time of stored charge carriers.