INVESTIGATION OF INTERFACE INTERMIXING AND ROUGHENING IN LOW-TEMPERATURE-GROWN ALAS/GAAS MULTIPLE-QUANTUM WELLS DURING THERMAL ANNEALING BY CHEMICAL LATTICE IMAGING AND X-RAY-DIFFRACTION

The effect of thermal annealing on the interface quality in undoped, AlAs/GaAs multiple quantum well (MQW) structures grown at a low substrate temperature (310 degrees C) by molecular beam epitaxy has been investigated using chemical lattice imaging and high resolution x-ray diffraction. The low-temperature-grown MQW is of high crystalline quality comparable to the standard-temperature-grown MQW. However, significant interface roughening and intermixing occurs at the quantum well heterointerface when the structures are annealed beyond 700 degrees C. The effective activation energy for interdiffusion is estimated as 0.24+/-0.07 eV. The structural properties observed here suggest that the excess arsenic associated with the low-temperature growth substantially enhances the diffusion of column III vacancies across an interface, which leads directly to intermixing of Al and Ga. (C) 1995 American Institute of Physics.