RECENT DEVELOPMENTS IN MOLECULAR-BEAM EPITAXY (MBE)

Semiconductor material research is motivated by the need for new devices which may improve the performance of a system. In turn, a new material technology may generate new devices and new technology. Molecular beam epitaxy (MBE) is a high-vacuum technique for the growth of epitaxial layers, usually semiconductors, that utilizes thermal beams of source atoms or molecules impinging on a single-crystal substrate. The ultrahigh vacuum nature of the process permits in situ metallization and growth of insulating materials on freshly grown semiconducting surfaces resulting in contamination-free interfaces. In situ Schottky barriers, nonalloyed ohmic contacts, and high-quality MIS structures have been grown with MBE. In addition, shadow masking techniques have been used to produce three-dimensional epitaxial structures on the substrate for possible monolithically integrated optical devices and patterned amorphous coatings have permitted the growth of isolated conducting islands of GaAs within a semi-insulating ''sea''. Ultrathin layered structures and superlattice structures have been grown and recently modulated doping of superlattice structures has yielded increased mobility anisotropic semiconductor material. This review is limited to recent developments in MBE of III-V compound and an extensive reference list is also included.