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Published online by Cambridge University Press: 11 February 2011
A contacted electroreflectance technique was used to characterize the electronic properties of AlGaN/GaN heterostructure field-effect transistors (HFETs). By studying variations in the electroreflectance with applied electric field, spectral features associated with the AlGaN barrier, the 2-dimensional electron gas at the interface, and bulk GaN were observed. Barrier-layer composition and electric field were determined from the AlGaN Franz-Keldysh oscillations. Comparing HFETs grown on SiC and sapphire substrates, the measured AlGaN polarization electric field (0.25±0.05 MV/cm) approached that predicted by a standard model (0.33 MV/cm) for the higher mobility HFET grown on SiC.