Room-temperature photoreflectance characterization of pseudomorphic GaAlAs/InGaAs/GaAs high electron mobility transistor structures including the two-dimensional electron gas density

Using contactless photoreflectance at 300 K the authors have characterized three pseudomorphic GaAlAs/InGaAs/GaAs high electron mobility transistor structures. The spectra from the InGaAs modulation-doped quantum well (MDQW) channel can be accounted for on the basis of a step-like two-dimensional density of states (screened exciton) and a Fermi level filling factor. A detailed lineshape fit makes it possible to evaluate the Fermi energy, and hence the two-dimensional electron gas concentration. Furthermore, other important parameters of the system such as built-in electric fields, In composition and well width of the InGaAs MDQW channel can be evaluated.