Effects of growth temperature and buffer scheme on characteristics of InP-based metamorphic InGaAs photodetectors

Abstract

A variety of metamorphic InGaAs photodetector structures have been grown on InP substrates by gas source molecular beam epitaxy. Their characteristics have been measured by atomic force microscopy, X-ray diffraction and photoluminescence to investigate the effects of growth temperature, grading profile and digital alloy intermediate layers in the buffer. The growth temperature is optimized to linearly decrease during the growth of InxAl1−xAs graded buffer, and kept at a relatively high temperature to grow the InGaAs absorption layer. The linearly grading profile of the composition in the buffer is superior to the convex grading profile, which indicates that the grading rate in the beginning could not be too high. The insertion of digital alloy intermediate layers in the InxAl1−xAs buffer improves the structural and surface qualities of the photodetector structures, whereas it introduces some negative effects on the optical quality.