Current state and future challenge in molecular beam epitaxy (MBE) research.

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 10microns wavelength have been demonstrated.