Mid-infrared GaSb-based SAM APD with hole-initiated multiplication

The III–V-Sb separate absorption and multiplication (SAM) avalanche photodiode (APD) devices optimized for hole-initiated impact ionization have been developed. The hole-initiated process was selected to benefit from minimal valence band offset between InAsSb absorber and AlGaAsSb multiplier sections. The heterostructure design of the device facilitated shallow mesa fabrication, thereby minimizing etched sidewall leakage current. We tested devices with varying widths of the multiplier sections, with the most effective performance observed in SAM APDs featuring a 300 nm-thick multiplier section. The devices had cutoff wavelength of ∼3.9 μm at 80 K and operated in a background limited regime up to ∼200 K. The avalanche breakdown voltage was approximately −17.7 V at 80 K, increasing with temperature at a rate of 9.7 mV/K. An efficient hole-initiated impact ionization process resulted in multiplication gain values nearing one thousand, leading to peak values of current responsivity exceeding 50 A/W. It was observed that extensive tunneling occurs within the bias range between punch-through and avalanche breakdown, presumably due to the penetration of the electric field into the narrow bandgap absorber.