Ye Zhenhua

Influence of hydrogenation on the dark current mechanism of HgCdTe photovoltaic detectors

The influence of hydrogenation on the dark current mechanism of HgCdTe photovoltaic detectors is studied. The hydrogenation is achieved by exposing samples to a H2/Ar plasma atmosphere that was produced during a reactive ion etching process. A set of variable-area photomask was specially designed to evaluate the hydrogenation effect. It was found that the current–voltage characteristics were gradually improved when detectors were hydrogenated by different areas. The fitting results of experimental results at reverse bias conditions sustained that the improvement of current–voltage curves was due to the suppression of trap assisted tunneling current and the enhancement of minority lifetime in the depletion region. It was also found that the dominative forward current was gradually converted from a generation–recombination current to a diffusion current with the enlargement of the hydrogenation area, which was infered from the ideality factors by abstraction of forward resistance–voltage curves of different detectors.

Progress on HgCdTe MBE for the application of IRFPAs

The progress on molecularbeam epitaxial growth of HgCdTe focusing on the requirements by the 3rd generation of infrared focal plane arrays are described. As large format HgCdTe IRFPAs demanded, the efforts on HgCdTe MBE on large area alternative substrates were presented, such as the improvement of crystalline quality, surface morphology, as well as Cd composition umiformity. The device fabrication on 512×512 MW and SW IRFPAs well demonstrated the performance of HgCdTe epi-layer. The studies of HgCdTe MBE on lattice-match substrates also were described, which were essential for the fabrication of LW and APD HgCdTe detectors. After growth condition optimized, the uniformity of epi-layer was greatly improved. On 10 mm HgCdTe/ZnCdTe( x =0.22), a typical value of FWHM of (422) X-ray diffraction was found to be less than 25 arcsec, as well as the best results of EPD reached 3×10 4 cm - 2 .

An Investigation on Spectral-Characteristic of HgCdTe two-color Detector

Some recent results of spectral-characteristic investigation on integrated HgCdTe infrared two-color detector are presented. Many discussions were focused on SWIR response of the preliminary two-color detector which exhibited a sharply peaked spectrum. The reason of SWIR abnormal spectrum was rooted out, and the way to solve the problem was obtained theoretically. Finally, the proper spectral responses of two-color detector with an improved structure were accomplished as expected.