A Monte Carlo study of gallium desorption kinetics during MBE of (100) GaAs/AlGaAs heterostructures

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In situ desorption mass spectrometry studies (DMS) of AlGaAs/GaAs molecular beam epitaxy (MBE) at high substrate temperatures reveals a rich transient behavior in the Ga desorption signal during the formation of the AlGaAs-on-GaAs interface. In this study we develop Monte Carlo (MC) models for Ga desorption, in which the effects of the Al-Ga interaction strength and the inclusion of an Al-Ga surface exchange mechanism are investigated. The models which best describe the experimental observations are identified. The transients in Ga desorption rate at the AlGaAs-on-GaAs interface and the experimentally observed reduction in Ga desorption energy during growth of AlGaAs are explained in terms of the reduction in V/III flux ratio accompanying the opening of the Al shutter. The proposed effects of this reduction in V/III flux ratio are consistent with the results predicted by the different models.