Organometallic vapor phase epitaxy of relaxed InPAs/InP as multiplication layers for avalanche photodiodes

Abstract

Abstract InP 1− y As y epitaxial layers grown lattice-mismatched (LMM) on InP substrates were investigated as a new materials system for multiplication layers in Geiger-mode avalanche photodiodes (GM APDs) for detection of photons in the range 1.6–2.5 μm. LMM InP 1− y As y epilayers were grown on semi-insulating (1 0 0) InP substrates misoriented 0.2° and 2°→[1 1 0] by organometallic vapor phase epitaxy at a growth temperature of 580 °C. The growth scheme used for the InP 1− y As y buffer layer was optimized based on surface step structure and X-ray diffraction. It was found that step-flow growth is a minimum criterion for obtaining good material quality. A narrower XRD full-width at half-maximum values were measured for 2°-miscut substrates compared to 0.2°-miscut substrates. A high-quality buffer was obtained by step-grading the InP 1− y As y composition in increments of y =0.05 over a layer thickness of 0.5 μm to a final y =0.25. The device performance of LMM GM APDs was compared to that of measured more traditional lattice-matched GaSb-based devices. At 77 K, dark count rates of LMM devices are ∼50 kHz at 5 V overbias, and are comparable to GaSb-based p–i–n diodes operated in Geiger mode, while reset times of 0.02 ms are approximately 3 orders of magnitude lower than GaSb-based GM APDs.