A Measurement Technology For HgCdTe Materials And Devices By Laser Beam Induced Current

Mercury cadmium telluride(HgCdTe) is one of the most important materials for infrared detector fabrication, among which HgCdTe photovoltaic detector is the main aspect. Array structure of the pn junction has a major impact on the performance and effectiveness of HgCdTe photovoltaic detector, thus the overall size of the pn junction is an important parameter for HgCdTe detector performance. In this paper, Laser Beam Induced Current(LBIC) test and I-V test were employed for measurement of pn junction outline dimension of p-type n +-on-p structure HgCdTe material. The main results and contents are as follows:1.The principle of LBIC method was investigated: The optical carriers were generated by the light excitation pn junction, and the current signal produced at the built-in electric field. LBIC test system was set up and met the requirements of the system accuracy successfully, which is the minimum laser spot diameter of 5?m,lowest test stepping of 1?m. Preliminary judgment of LBIC test system was conducted to make sure of that the results comply with a standard the actual value.The influence of the spot diameter and scanning stepper for measurement accuracy of LBIC system was studied and found that the impact of the spot diameter on the measurement accuracy is not great, while a smaller scanning stepper step could bring about a more accurate measurement result within a certain range.2.Dry-etched HgCdTe material was measured by LBIC test for outline dimensions for pn junction and found that the longer dry etching, the deeper of inversion layer and more etching induced damage of pn junction expansion. Within a certain range, the extend region of pn junction was approximate linear correlation with etch pit depth. It was found after heat treatment of 2.5min at 180 ?, the pn junction area did not show significant further expansion, comparing to the results of the etched material before heat treatment. Comparing LBIC measurements with I-V measurements, we found consistent with the results obtained by the two methods, and more comprehensive information about pn junction of sample could obtained by LBIC system.3.Hg vacancy doped p-type HgCdTe material was measured by LBIC test and I-V test for outline dimensions for pn junction and found a smaller scale-range of pn junction area induced by implantation damage, but scale-range of pn junction extendafter heat treatment of 2.5min at 180 ?. In/Au-doped p-type HgCdTe material was also measured by LBIC test for outline dimensions for pn junction and found a larger scale extension of pn junction area induced by implantation damage, comparing with Hg vacancy doped p-type HgCdTe material. We deduced that it was because of the instability and accumulation of Au near the surface of HgCdTe material. And after different time of heat treatment, the results indicated that the depth and scale-range of pn junction becomes larger with the increase of heat treatment time.