The growth of CMT on GaAs for high quality linear arrays of MWIR and LWIR photodiodes

Abstract

High quality MWIR and LWIR linear photodiode arrays of greater than 100 elements have been fabricated by mercury diffusion in MOCVD grown (111)CMT/GaAs and (100)CMT/GaAs. The (100)CMT layers were grown on a variety of buffers, whilst CdTe was used for (111)CMT growth. Optimisation of the growth conditions led to the (100) layers being p-type as grown, with FWHMs as low as 80 arc sec. The detector geometry was a linear array of 100×60 or 30×30 μm2 optical areas. State-of-the-art diode results have been obtained in both (100)CMT and (111)CMT, at MWIR and LWIR. A 120 element array of 11.4–12.7 μm cut-off photodiodes had typical 77 K R0A's of 2–10 ω cm2 and detectivities of about 1×1011 cm Hz1/2 W-1. MWIR yields were typically 90% for (111) and 95% for the hillock free regions of the (100)CMT. LWIR yields of 95% have been obtained for (100)CMT.