A preliminary study on MBE-grown HgCdTe two-color FPAs

This paper presents the recent progress on the study of device processings at multilayer HgCdTe film for integrated two-color (SWIR/MWIR) n-p-P-P-N detector arrays. The four-layer p-P-P-N heterostructures Hg1-xCdxTe film needed to achieve two color detector arrays was grown by molecular beam epitaxy (MBE) on (211)B oriented GaAs substrates. The secondary ion mass spectroscopy (SIMS) data for the HgCdTe film was obtained. The p-type layer on top of a thin P-type potential barrier layer and the SWIR P-on-N homojunction photodiode formed in-situ during MBE growth using indium impurity doping was processed into the MWIR planar photodiode by selective B+-implantation. The preliminary 256×1 linear arrays of SWIR/MWIR HgCdTe two-color FPAs detector were then achieved by mesa isolation, side-wall passivation and contact metallization. At 78K, the average R0A values of SWIR and MWIR are 3.852×105 Wcm2 and 3.015×102 Wcm2, and the average peak detectivities Dλp* are 1.57×1011cmHz1/2/W and 5.63×1010 cmHz1/2/W respectively. The SWIR photodiode cut-off wavelength is 3.04μm and the MWIR photodiode cut-off wavelength is 5.74μm, quite consistent with the initial device design. The SWIR response spectrum of the two-color detector with a distinct fall-off at shorter wavelength regime was discussed especially.