HG1-XCDXTE METAL-SEMICONDUCTOR-METAL (MSM) PHOTODETECTORS

Metal-semiconductor-metal (MSM) detectors with active layers of Hg1-xC dxTe (x = 0.62-0.74) and electrode spacings of 2, 4, and 6 pm have bee n fabricated and characterized. Direct-current measurements have shown that the detectors exhibited a low dark current (ranging from 0.94 mA /cm2 for 6-mum electrode spacings to 3.54 mA/cm2 for 2-mum spacings at x = 0.70) and high responsivity from 0.15 to 1.5 A/W at 10-V bias. Th e lowest values of dark current (0.16 mA/cm2) were obtained for those Hg1-xCdxTe detectors which incorporated an overlayer of CdTe. For Hg1- xCdxTe detectors without the overlayer, increasing in Cd mole fraction (x) resulted in a decrease in the dark current and a reduction in the 300-nm responsivity of the devices. Measurements of frequency respons e for these detectors show a maximum loss of 8 dB to 20 GHz. These res ults compare favorably with high-performance MSM detectors based on In 0.53Ga0.47As with a lattice-matched barrier layer of In0.52Al0.48As.