Study of junction performance in mid-wavelength HgCdTe photodiodes by laser beam-induced current microscope

Abstract

This paper reports on the disappearance of photosensitive area extension effect and the novel temperature dependence of junction performance for mid-wavelength HgCdTe detectors. The performances of junction under different temperatures are characterized by laser beam induced current (LBIC) microscope. The physical mechanism of temperature dependence on junction transformation is elaborated and demonstrated using numerical simulations. It is found that Hg-interstitial diffusion and temperature activated defects jointly lead to the p-n junction transformation depended on temperature, and wider band gap compared with the long-wavelength HgCdTe photodiode may correlate with the disappearance of photosensitive area extension effect.1 INTRODUCTION Mercury cadmium telluride (HgCdTe) is widely used in the fabrication of various infrared detectors for military and civil purposes, 1-3 However, the performance of HgCdTe IRFPAs is still easily affected by different defects and complex doping mechanism in the manufacturing process. 4-5 Any nonuniformity specifications often limit the yield of devices in large HgCdTe-based infrared arrays, which results in low yields and high cost. Currently, Laser-beam-induced-current (LBIC) measurements as a high-resolution, nondestructive optical technique have been applied to providing spatially resolved information about electrically active defects and localized nonuniformities in HgCdTe IRFPAs at intermediate processing stage, 6-7 which could significantly promote efficiency and save costs.Some researchers 8 found that there was n-type inversion region extension in different long-wavelength HgCdTe photodiodes formed by B + ion implantation at low temperature (87K) comparing with that at room temperature (300K). In this paper, the temperature dependence of junction performance for mid-wavelength HgCdTe arrays is characterized by the LBIC technique. We find that the photosensitive areas under different operating temperature are approximately the same size, which demonstrated the disappearance of such extension effect. At the same time, the polarity inversion of