Small Two-Dimensional Arrays of Mid-Wavelength Infrared HgCdTe Diodes Fabricated by Reactive Ion Etching-Induced p-to-n Type Conversion

The reactive ion etching (RIE) technique has been shown to produce high-performance n-on-p junctions by localized-type conversion of p-type mid-wavelength infrared (MWIR) HgCdTe material. This paper presents variable area analysis of n-on-p HgCdTe test diodes and data on two-dimensional (2-D) arrays fabricated by RIE. All devices were fabricated on x = 0.30 to 0.31 liquid-phase epitaxy (LPE) grown p-type (p = similar to1 X 10(16) cm(-3)) HgCdTe wafers obtained from Fermionics Corp. The diameter of the circular test diodes varied from 50 mum to 600 mum. The 8 x 8 arrays comprised of 50 mum x 50 mum devices on a 100-mum pitch, and all devices were passivated with 5000 Angstrom of thermally deposited CdTe. At temperatures > 145 K, all devices are diffusion limited; at lower temperatures, generation-recombination (G-R) current dominates. At the lowest measurement temperature (77 K), the onset of tunneling can be observed. At 77 K, the value of 1/R(0)A for large devices shows quadratic dependence on the junction perimeter/area ratio (P/A), indicating the effect of surface leakage current at the junction perimeter, and gives an extracted bulk value for R(0)A of 2.8 x 10(7) Omega cm(2). The 1/R(0)A versus P/A at 195 K exhibits the well-known linear dependence that extrapolates to a bulk value for R(0)A of 2 17.5 Omega cm(2). Measurements at 77 K on the small 8 x 8 test arrays were found to demonstrate very good uniformity with an average R(0)A = 1.9 x 10(6) Omega cm(2) with 0degrees field of view and D* = 2.7 x 10(11) cm Hz(1/2)/W with 600 field of view looking at 300 K background.