INDIUM LAYERS IN LOW-TEMPERATURE GALLIUM-ARSENIDE - STRUCTURE AND HOWIT CHANGES UNDER ANNEALING IN THE TEMPERATURE-RANGE 500-700-DEGREES-C

Transmission electron microscopy is used to study the microstructure o f indium delta layers in GaAs(001) grown by molecular beam epitaxy at low temperature (200 degrees C). This material, referred to as LT-GaAs , contains a high concentration (approximate to 10(20) cm(-3)) of poin t defects. It is established that when the material is delta-doped wit h indium to levels equivalent to 0.5 or 1 monolayer (ML), the roughnes s of the growth surface leads to the formation of InAs islands with ch aracteristic lateral dimensions < 10 nm, which are distributed primari ly within four adjacent atomic layers, i.e., the thickness of the indi um-containing layer is 1.12 nm. Subsequent annealing, even at relative ly low temperatures, leads to significant broadening of the indium-con taining layers due to the interdiffusion of In and Ga, which is enhanc ed by the presence of a high concentration of point defects, particula rly V-Ga, in LT-GaAs. By measuring the thickness of indium-containing layers annealed at various temperatures, the interdiffusion coefficien t is determined to be DIn-Ga = 5.1 x 10(-12) exp(-1.08 eV/kT) cm(2)/s, which is more than an order of magnitude larger than DIn-Ga for stoic hiometric GaAs at 700 degrees C. (C) 1998 American Institute of Physic s.