Interlayer formation due to group V-hydride stabilization during interruptions of MOVPE growth of InGaP

Abstract

The effect of indium and arsenic carry-over and of arsenic–phosphorus exchange on unintentional interlayer formation due to prolonged stabilization under arsine or phosphine during InGaP growth interruptions in metalorganic vapour phase epitaxy (MOVPE) at 580 °C is investigated. Photoluminescence, x-ray diffraction, secondary ion mass spectrometry, transmission electron microscopy and capacitance–voltage (C–V) depth profiling of the electron concentration are used to detect and to characterize possible unintentionally formed interlayers. The C–V measurements show that purging with PH3 mainly enhances the degree of ordering of an interlayer region due to a P-rich reconstruction of the InGaP surface during the growth interruption. The interlayer stress and band offset are too small to be detected by x-ray diffraction or photoluminescence. In contrast, purging with AsH3 during InGaP growth interruption leads to strong arsenic incorporation, but does not lead to any change in the In concentration. The As-rich interlayer gives rise to additional photoluminescence peaks and compressive strain. The relatively large interlayer thickness detected by C–V and SIMS measurements of up to 20 nm indicates that arsenic accumulated during the prolonged growth interruptions carries over into the InGaP layer grown after the interruption. It is shown that the chosen growth conditions suppress the In carry-over, but As carry-over occurs additionally to the As–P exchange.