IN-SITU AND EX-SITU SPECTROSCOPIC INVESTIGATION OF LOW-TEMPERATURE-GROWN GALLIUM-ARSENIDE BY MOLECULAR-BEAM EPITAXY

Low temperature growth of GaAs not only provides useful semi-insulatin g layers in a variety of devices, but also is interesting from a mater ials and crystal growth point of view. In this work we have utilized a n in situ spectroscopic ellipsometer having 44 wavelength regions in t he range 4000-8000 Angstrom to monitor the low temperature growth of G aAs. Several different regions of growth have been observed, in agreem ent with earlier studies utilizing single wavelength ellipsometry. An initial region of homogeneous growth is followed by regions of materia l that exhibit varying optical properties. The complex refractive inde x of the epitaxial LT-GaAs films have been extracted from the real-tim e data acquired during the homogenous growth region. Ex situ character ization of these films was performed using high-resolution x-ray diffr action to determine the excess As concentration. Films in which the lo w temperature growth was stopped within the homogeneous growth regime have been characterized with a multiwavelength variable angle ellipsom eter, and the complex refractive index of these films in the range 400 0-17000 Angstrom have been extracted. (C) 1996 American Vacuum Society .