Molecular-beam epitaxy flux transient monitoring and correction using in situ reflection mass spectrometry

The use of reflection mass spectrometry (REMS) for in situ monitoring of group III flux transients during molecular‐beam epitaxial growth is reported. Normal shutter closure caused effusion cell heating which resulted in flux overshoots of up to 30%. The variation of the magnitude and time constant of the overshoot, as a function of group III material and shutter closed time, was determined for our Riber 2300 system. It was verified that the observed REMS transients corresponds to growth transients using photoluminescence and transmission electron microscopy analysis of GaAs/AlGaAs and InGaAs/InAlAs multiple quantum well (MQW) structures. Flux transient correction during GaAs/AlGaAs MQW growth was accomplished by ramping the temperature of the Ga effusion cell, based on our previous analysis of the transients.