Using room temperature photoreflectance (PR) we have characterized the properties of three GaAlAs/InGaAs/GaAs high electron mobility transistor structures with two different well widths fabricated by molecular beam epitaxy on (001) GaAs substrates. The samples were denoted as #1, #2, and #3 with well widths of 140, 160, and 160 Å, respectively. Samples #2 and #3 were grown on substrates with different threading dislocation densities. For the latter two samples the well width exceeds the pseudomorphic limit so that there are some strain relaxation and related misfit dislocations as determined from the x-ray measurements. In order to detect the anisotropic strain of the misfit dislocations related to strain relaxation, the PR measurements were performed for incident light polarized along  and  directions. Evidence for the influence of the strain relaxation upon the relaxed channel was provided by the observed anisotropy of the polarized PR signal in the InGaAs channel layer. Signals have been observed from every region of the sample, making it possible to evaluate the In and Al compositions, channel width and two-dimensional electron gas density, as well as the properties of the GaAs/GaAlAs multiple quantum well buffer layer.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)