MOLECULAR-BEAM EPITAXIAL-GROWTH OF IN0.65GA0.35AS QUANTUM-WELLS ON GAAS SUBSTRATES FOR 1.5 MU-M EXCITON RESONANCE

A novel approach of growing high quality In0.65Ga0.35As mutiple quantum wells (MQWs) with Al0.33Ga0.67As barriers on GaAs substrates by molecular beam epitaxy (MBE) is reported for optical devices operating near 1.5 mum at room temperature. Operation at 1.5 mum requires InGaAs QWs with very large lattice mismatch to the GaAs substrates (4.7% in this study). The best quality MQWs were achieved by adding one monolayer of GaAs smoothing layers with growth interruptions at the interfaces of both sides of the InGaAs wells and by growing at a very low temperature (280-degrees-C) compared to the buffer layers and typical InGaAs layer growth temperatures (450-degrees-C). The MQW region was grown on a linearly-graded InGaAs buffer layer with a 10%/mum grading rate which was fully relaxed, very smooth, and completely defect-free at the top region. This sample showed a sharp exciton peak near 1.5 mum at room temperature. Cross-section transmission electron microscopy (XTEM), four crystal X-ray diffractometry, and optical absorption measurement were used to characterize the MQW structures.