Photoreflectance studies of surface state density of InAlAs

The surface barrier height and surface Fermi level of InAlAs were investiga ted via photoreflectance spectra. Surface state density was then determined from the surface barrier height as a function of temperature, illumination power intensity, and intrinsic layer thickness. Results obtained from thes e three independent approaches all give the same conclusion, that the surfa ce states are distributed over two separate regions within the energy band gap. Closely examining the photovoltage induced by various incident beam in tensities revealed that the photovoltage effect is negligible when the illu mination power intensity is below 1.0 muW/cm(2). (C) 2001 American Institut e of Physics.