LTMBE GAAS - PRESENT STATUS AND PERSPECTIVES

When GaAs is grown via MBE at 200 degrees C (compared to the normal 58 0-600 degrees C), the films manifest a remarkable set of structural, e lectrical and optical properties. As grown, LT GaAs (as it is commonly known) has an excess of As, contains a high concentration of point de fects, displays hopping band conductivity and shows little, if any, ph otoluminescence. After a 600 degrees C anneal, the layers have a relax ed lattice constant, are highly resistive and contain a distribution o f As precipitates. The point defect concentration diminishes by severa l orders of magnitude. The photo-induced carrier lifetime typically is of the order of 200 fs. This account will review what is known about these interesting materials, discuss models to explain the transport p roperties and mention potential applications.