Contactless electroreflectance study of band gap renormalization for Mg-doped GaN

Abstract

The energy gap of GaN : Mg films with various Mg concentrations was studied by contactless electroreflectance (CER) spectroscopy at room temperature. A clear and well-defined CER resonance was observed for all GaN : Mg layers. This resonance has been attributed to band-to-band absorption without any excitonic contributions. Analysing the shape and energy of this resonance, it has been concluded that the incorporation of Mg atoms into GaN film changes the surface band bending and reduces the energy gap. The band gap renormalization coefficient for the GaN : Mg layers has been determined to be (1.9 ± 0.2) × 10−8 eV cm.