Temperature-dependent contactless electroreflectance and photoluminescencestudy of GaAlAs/InGaAs/GaAs pseudomorphic high electron mobility transistor structures

Temperature-dependent contactless electroreflectance (CER) and photolumines cence (PL) measurements in the range of 30 K <T < 300 K on two GaAlAs/InGaA s/GaAs pseudomorphic high electron mobility transistor structures with diff erent well widths fabricated by molecular-beam epitaxy on (100) GaAs substr ates are presented. For the CER measurement, the 11H transition is complete ly screened out by the two-dimensional electron gas and the prominent featu re related to the Fermi energy edge singularity transition showed a Stokes shift to higher energy with respect to the 21H transition of the PL measure ments at low temperature. From the Stokes shifts, the Fermi energy level of the system is evaluated, and hence, the density of the two-dimensional ele ctron gas. The temperature-dependent PL measurements revealed two features, identified to be the 11H and 21H transitions. The relative intensities of the 11H and 21H transitions were analyzed taking into account the effect of the subband filling and the wave-function overlap factors. A good agreemen t is found between experimental data and theoretical calculation results. ( C) 2001 American Institute of Physics.