An analysis of temperature dependent piezoelectric Franz-Keldysh effect inAlGaN

Strong Franz-Keldysh oscillations near the band gap of AlGaN are observed i n the contactless electroreflectance (CER) studies of a GaN/InGaN/AlGaN mul tilayer structure. The line shape analysis of the CER spectra at different temperatures provides an accurate determination of the AlGaN band gap energ ies and the built-in electric fields. Using the existing data of the therma l expansion coefficients of GaN and sapphire, and the piezoelectric constan ts of AlGaN, the temperature dependence of the electric field is estimated and is in good agreement with the experimental results between 15 and 300 K . We attribute such electric field to the piezoelectric strain effect. (C) 2000 American Institute of Physics. [S0003-6951(00)02308-1].