CHARACTERIZATION AND IMPROVEMENT OF THE LAYER UNIFORMITY FOR LARGE-AREA QUANTUM-WELL DEVICE ARRAYS GROWN IN AN INTEVAC VARIAN GEN-II MOLECULAR-BEAM EPITAXY SYSTEM

The uniformity of GaAs, AlAs, and InAs grown in an Intevac/Varian Gen II molecular beam epitaxy system has been characterized using a quantu m well (QW) structure and room-temperature photoluminescence (PL) eval uation. Artifacts in the measured distributions have been identified t hrough simulations and were proposed to originate from incomplete rota tion averaging during growth of the QW and/or oscillations of the Al m ole fraction in the growth direction. The first effect is an actual th ickness variation while the second effect leads to shifts in the PL si gnal that will be incorrectly interpreted as thickness variations when Schrodinger's equation is solved for wells with symmetric potential b arriers. Modeling of the flux distribution predicted that an upward ti lt of the substrate away from the group III cells is beneficial. This was confirmed experimentally with the best overall uniformity achieved for a tilt of approximately 9 deg.