Influence of low-temperature chemical vapor deposited SiO2 capping layer porosity on GaAs/AlGaAs quantum well intermixing

Plasma-enhanced chemical vapor deposition of SiO2 at temperatures below 300 degrees C was used in conjunction with rapid thermal annealing for quantum well intermixing. Variable blue shifts of up to similar to 200 meV were ob served while still maintaining clearly resolved exitonic behavior. The ener gy shifts were similar for capping layers deposited below 200 degrees C, wh ich were significantly higher than those obtained for SiO2 layers deposited at 300 degrees C. We demonstrate that the increased porosity of SiO2 cappi ng layers deposited below 200 degrees C is responsible for the enhanced int ermixing. The evidence for porosity-enhanced intermixing was obtained from spectroscopic ellipsometry, Fourier transform infrared spectroscopy, and P- etch rate measurements. (C) 2000 The Electrochemical Society. S1099-0062(99 )11-110-6. All rights reserved.