HgCdTe mid-wavelength IR photovoltaic detectors fabricated using plasma induced junction technology

Preliminary characterization results are presented for mid-wave infrared (M WIR) mercury cadmium telluride n-on-p photodiodes fabricated using a plasma induced type conversion junction formation technology. The diodes have bee n fabricated on three different vacancy doped p-type epitaxial starting mat erials, grown by liquid phase epitaxy (LPE) on CdZnTe, LPE on sapphire, and P/p isotype heterojunction material grown by molecular beam epitaxy (MBE) on CdZnTe. All materials had CdTe mole fraction in the active region of the device of similar to 0.3. The process uses a H-2/CH4 plasma generated in a parallel plate reactive ion etching (RIE) system to type convert the p-typ e material to n-type. The process is different from previously reported typ e conversion techniques in that it does not require a high temperature anne al, does not expose the junction at the surface to atmosphere after formati on, and requires significantly fewer process steps than other planar proces ses. Homojunction devices fabricated using this process exhibit R(0)A value s > 10(7) Ohm.cm(2) at 80 K. The R(0)A is diffusion limited for temperature s > similar to 135 K. Results for responsivity, bias dependence of dynamic resistance -junction area product and 1/f noise show that the resulting dio des are comparable to the best planar diodes reported in the literature.