Comparison and analysis of Al0.7InAsSb avalanche photodiodes with different background doping polarities

Abstract

Background doping polarity is a key parameter in the design of numerous electrical and optoelectronic devices. It is especially critical for avalanche photodiodes (APDs). Recently, high-performance APDs have been demonstrated based on the AlInAsSb digital alloy materials system. A critical element of this work was the determination of the background doping polarity of the molecular beam epitaxial grown wafers. In this work, we determine the unintentional background doping polarity of Al0.7InAsSb using the double mesa capacitance-voltage technique. We fabricated two p-i-n Al0.7InAsSb structures: one with p-type background polarity and the other with n-type. The measurements indicate that devices with different background doping polarities show different capacitance relations to the mesa diameters; moreover, the relationship reverses at high voltage in a p-type background device. Subsequent simulations reveal that this reversal is caused by electrical field confinement after the depletion reaches the smaller top mesa. These findings are consistent with reports of reduced surface leakage current in double and triple mesa structures.