Temperature analysis of dark current in pin-photodiodes based on In$_{0.83}$Ga$_{0.17}$As/InP epitaxial heterostructures with metamorphic buffer layers

Crystals of 2.2–2.6 $\mu$m sensitive PIN-photodiodes were fabricated by lift-off photolithography using InAlAs/In$_{0.83}$Ga$_{0.17}$As/InP heterostructures, grown by molecular beam epitaxy. A design feature of the proposed heterostructures is the inclusion of metamorphic InAlAs buffer layers for subsequent low-stress growth of the In$_{0.83}$Ga$_{0.17}$As active region. A profile of charge carrier distribution over the structure was obtained employing electrochemical capacitance-voltage characteristic, and the carrier concentration of 2.5$\cdot$10$^{16}$ cm$^{-3}$ in the In$_{0.83}$Ga$_{0.17}$As active layer was determined. Dark current-voltage characteristics of pin-photodiode chips from the same wafer with typical ($\sim$2 mA/cm$^2$ at -10 mV) and excessive ($\sim$3 mA/cm$^2$ at -10 mV) values of dark currents were studied in the temperature range of 80–300 K. Connection of the dark current mechanisms associated with threading dislocations in the photodiode active region with increased dark current densities was demonstrated in the reverse bias voltage range of 0.3–1 V. With a small applied bias of -10 mV, the dominant contribution of trap-assisted tunneling and surface recombination at temperatures of 180–240 K and generation-recombination of charge carriers in the space-charge region at 260–300 K to the overall dark current was found in both photodiode chip samples.