Current state and future challenge in Molecular Beam Epitaxy (MBE) research

Abstract

Molecular beam epitaxy (MBE) has reached a state where a whole new generation of microwave and optoelectronic devices are being fabricated. Artificially structured materials have been prepared with ultra-thin layered structures or with delta doping resulting in “band-structure engineering”. New resonant tunneling and quantum-well devices, such as frequency multipliers, logic circuits, optical switches, and high quality GaAs/AlGaAs superlattice detectors operating at 3 to 10 μm wavelength have been demonstrated. Advances in MBE group IV elements include the growth of pinhole-free Si-silicide structures, single crystal SiO x, and Si/Ge xSi 1-x/Si heterostructure devices. There have been exciting results in II-VI compounds, and lasing action at visible wavelength was observed for the first time. Under a manufacturing environment, the typical thickness variation is 1.5% over a 3 inch GaAs wafer with solid source MBE. The wafer-to-wafer variation is 3%. Fifty-seven percent of the wafers have only 100–300 defects per cm 2 and the best has only 30 defects per cm 2. The future challenges in MBE are automation and high throughout. For gas-source MBE, it is important to develop non-toxic and high purity gas sources for manufacturing environments.