Response time study in unbiased long wavelength HgCdTe detectors

Theoretical and experimental investigations on the response time improvement of unbiased long-wave infrared (LWIR) HgCdTe detectors operating at temperatures T=230 K were presented. Metal–organic chemical vapor deposition technology is an excellent tool in fabrication of different HgCdTe detector structures with a wide range of composition and donor/acceptor doping and without postgrown ex-situ annealing. The time constant is lower in biased detectors due to Auger-suppression phenomena and reduction of diffusion capacitance related to a wider depletion region. The relatively high bias current requirements and excessive low-frequency noise, which reduces the detectivity of biased detectors, inspire research on the time constant improvement of unbiased detectors. The response time of high-operating temperature LWIR HgCdTe detectors revealed complex behavior being dependent on the applied reverse bias, the operating temperature, the absorber thickness and doping, the series resistance, and the electrical area of the devices. The response time of 2 ns was achieved for unbiased 30×30 μm HgCdTe structures with λ50%=10.6 μm operating at T=230 K.