InAsSb and InGaAs linear and focal-plane arrays

Short-wave IR and mid-IR photovoltaic detector arrays consisting of In(Ga)As and InAsSb were realized. Maximum array size is 256×256 elements on a 25 micron pitch. The layers were grown on 3 inches semi-insulating GaAs substrates by MBE thereby avoiding the need for substrate removal by wafer thinning after hybridization. A reliable and uniform detector process using improved wet-etching has been developed. The citric-acid based etch has been optimized for minimum underetch such that high fill factor is achieved even with a mesa-type process. Typical R_oA products at room temperature are within a factor of 2 of the theoretical limit for bulk leakage currents. The hybridization with silicon readout circuits consisted of Si-postprocessing by electroless plating or lithographic definition of Ni/Au, indium bump electroplating on the III-V chip and flip-chip integration with individual indium bumps. The indium bump process resulted in 13 micron diameter solderbumps which allows pixel pitches below 20 micron.