Determination of doping polarity of unintentionally doped antimonide avalanche photodiodes on InP substrate

Background doping polarity type is a critical parameter for avalanche photodiode performance. We demonstrated a technique using capacitance-voltage (CV) measurements on double mesa structures with a p-i-n or n-i-p homojunctions to determine the polarity type of the unintentionally doped intrinsic (uid) region. CV measurements scale with the size of the mesa and enable design flexibility in producing variable top or bottom mesa diameters. We designed and tested AlGaAsSb and AlInAsSb structures and performed measurements at varying temperatures. Measurements varied with the top mesa, indicating the p-n junction is located between the p-region and the uid region, therefore it is n-type.