Effects of in-situ thermal annealing on metamorphic InGaAs photodetector materials grown by molecular beam epitaxy

The optoelectronic, morphological and structural performances of metamorphic In0.75Ga0.25As photodetector materials treated by in-situ thermal annealing were investigated. The samples were annealed with different temperatures and maximum temperature durations. The photoluminescence intensity of the samples with increasing the annealing temperature or prolonging the maximum temperature duration significantly increased compared to the as-grown sample, and the highest photoluminescence intensity was reached by in-situ thermal annealing at 690 degrees C for 20 s and at 630 degrees C for 120 s, respectively. The surface roughness and uniformity was deteriorated by in-situ thermal annealing. The dark currents of the fabricated photodetector chips were characterized and the results indicated that the dark current was affected by dislocation density and surface roughness. The sample of prolonging in-situ thermal annealing maximum temperature duration showed more detrimental effect on photoluminescence and dark current performances than that of increasing annealing temperature due to the enhanced surface roughness and disorder. These results indicate that partial in-situ thermal annealing treatment has improved the quality of metamorphic InGaAs photodetector materials and devices.