Ultra High Vacuum Processing: MBE

Abstract

As an ever increasing variety of processing steps are being performed in vacuum or vacuum-based environments, and as pressures for finer control and higher reproducibility drive these vacuums toward the ultra high vacuum (UHV) range, the combination of UHV processing and UHV semiconductor crystal growth by molecular beam epitaxy (MBE) entirely in an interconnected UHV environment becomes increasingly attractive. In this paper we discuss three examples of such combinations of MBE and processing, each of which yields unique structures unobtainable by combinations of conventional processing and crystal growth. In the first, we combine MBE and refractory metal evaporation to produce buried metal layers in III-V materials for use as buried gates and metal interconnects. In the second, we add plasma etching to produce selective area growth on substrates by means of a technique called tungsten patterning which opens up the possiblity of growing different layer structures at different points on the wafer for possible integration of more than one type of device on the same optoelectronic integrated circuit. And in the third, we invert the order of growth and patterning to produce superlattice structures grown on patterned substrates which, due to the lateral variation in superlattice period, offer possibilities of varying index of refraction and effective bandgap laterally across the wafer.