Peculiarities of photoluminescence of vertical n + /n -GaAs/Al0.25 Ga0.75 As MBE- and MOCVD-grown structures designed for microwave detectors

Abstract

Vertical MBE- and MOCVD-grown n+/n-GaAs/Al0.25Ga0.75As structures used for microwave electronics have been studied with continuous wave and timecorrelated single photon counting dynamic photoluminescence technique. The photoluminescence spectra and light emission lifetimes are used to explain the recombination mechanisms of the excited carriers. This paper presents results showing the differences in recombination characteristics of n+-Al0.25Ga0.75As layers grown using MBE process compared with MOCVD process. One of these differences is that the PL spectrum of the MOCVD-grown layer is shifted towards the forbidden energy gap region, as well as the characteristic recombination time is longer than for the MBEgrown sample. This peculiarity can be attributed to the formation of the localised band tails in the n+-Al0.25Ga0.75As MOCVD-grown sample. The proposed analytical model explains the differences in microwave detection properties of the samples grown by MBE and MOCVD processes.