Epitaxial Growth of GaAs in Deep Dielectric Windows Using Solid Source Molecular Beam Epitaxy

摘要

An improved epitaxial growth process for GaAs in deep dielectric windows (DDW) is reported. The growth was carried out on (100)-oriented semi-insulating (SI) GaAs substrate at ~520°C by solid source molecular beam epitaxy (SSMBE) using a valved arsenic cracker source. Dielectric stacks with 10 periods of alternating silicon nitride (2000A) and silicon dioxide (l000A) layers were deposited using plasma enhanced chemical vapor deposition (PECVD) for the formation of deep (3 μm) dielectric windows. The alternating dielectric layer stack has been shown to be of greater stability than a single dielectric layer for the purpose of forming the DDW. A process of fabricating the DDW structures, which eliminates possible contamination at the growth area during photoresist patterning and removing, and subsequent etching of the DDW, has resulted in improved epitaxial layer quality. Micro-Raman spectroscopy measurements showed a significant increase in the longitudinal-optic (LO) to transverse-optic (TO) signal intensity ratio (I_(LO/TO)) from ～4.0 to ～16.0 of the first-order Raman line of GaAs. Supporting evidence from low temperature (4K) photoluminescence (PL) showed a reduction in intensity of the conduction band to neutral carbon acceptor (e-C°) emission by a factor of 4.5. This suggests lower levels of carbon contamination originating from the improved fabrication process of the DDW. Scanning electron microscopy (SEM) images showed smooth surface morphology of the GaAs inside the DDW area. These results have important implications on the process of MBE regrowth for optoelectronics integration.