Analysis of crosstalk in HgCdTe p-on-n heterojunction photovoltaic infrared sensing arrays

In this paper, an experimental and theoretical study is carried out of cros stalk between nearest-neighbor devices within a backside-illuminated linear HgCdTe photovoltaic infrared sensing array. The dominant form of crosstalk that occurs in high performance photovoltaic arrays is associated with pho togenerated minority carriers that diffuse laterally between adjacent devic es within the array. To measure crosstalk, a scanning laser microscope is u sed to obtain a spatial map of spot-scan photoresponse at a temperature of 80K for individual p-on-n photovoltaic devices within the linear array. The se experimental results are compared to calculations performed on a commerc ial two-dimensional device simulation package. The crosstalk measurements a nd calculations presented in this paper include results on mid-wavelength i nfrared planar device structures, as well as long-wavelength infrared mesa- isolated devices, which give measured crosstalk values of 6.2 and 8.3%, res pectively. The results indicate that the device simulations are in good agr eement with experimental results. Further simulations are carried out to de termine the sensitivity of crosstalk to various material and device paramet ers such as epitaxial layer thickness (7 to 25 mu m), illumination waveleng th (1.047 to 11.0 mu m), minority carrier diffusion length (8 to 90 mu m), and diode pitch. It is found that the dominant feature influencing the valu e of crosstalk is the distance between the region of photogeneration and th e collecting p-n junction.