Investigation of Anomalous Optical Characteristics of InGaAsP Layers on GaAs Substrates Grown by Metalorganic Vapor Phase Epitaxy

Abstract

We investigated the growth of InGaAsP layers on GaAs substrates by metalorganic vapor phase epitaxy (MOVPE) for application in optical devices. Anomalous large redshifts of photoluminescence (PL) were observed for samples of specific In 1Àx Ga x As y P 1Ày compositions (x and y are approximately 0.85 and 0.65, respectively). We showed that these large redshifts were induced by phase separation in the miscibility gap of InGaAsP. In order to clarify the threshold value of the phase separation that causes this anomalous PL emission, the phase separation was quantified by combining PL spectroscopy and energy dispersive X-ray spectroscopy (EDX). It was found for the first time that PL redshifts start to occur when the phaseseparation quantity of the group-III element of In 1Àx Ga x As y P 1Ày crystals (Áx) exceeds $0:05. Such large PL redshifts can be attributed to the emission from defect-related energy levels caused by phase separation.

Coexistence properties of phase separation and CuPt-ordering in InGaAsP grown on GaAs substrates by organometallic vapor phase epitaxy

“…These results revealed that the degree of the CuPt-ordering in InGaAsP with a low arsenic content was significantly enhanced in the 630 1C-grown sample. The results for CuPt-ordering in the TED patterns are consistent with those in the photoluminescence measurements reported previously [14][15][16][17].…”

“…A coarse tweed structure with alternating bright/dark contrast along the growth direction was observed in the 022 micrographs (upper side). The coarse tweed structure has been experimentally confirmed to be an LCM formation [9,17]. As for InGaAsP, it has been reported that the 022 micrographs showed strong contrast due to the LCM, but the 200 micrographs showed only weak contrasts along with small composition variations [11,13].…”

“…We have focused on the generation mechanism of immiscibility in OMVPE grown InGaAsP on GaAs substrates and performed systematic studies [14][15][16][17]. In previous studies, we have reported on the suppression of the phase separation in the OMVPE grown InGaAsP with low arsenic contents and attributed the suppression to the surface reconstructions such as P(2 Â 4), which is the origin of CuPt-ordering [15].…”