Microcalorimetric absorption spectroscopy in GaN-AlGaN quantum wells

Microcalorimetric measurements of small absorption coefficients have been p erformed on thin GaN-AlGaN quantum wells grown by Reactive Molecular Beam E pitaxy on Al2O3 substrates. In addition to strong absorption at the energy of the GaN buffer and at the energy of the thick AlGaN barrier layers, we c ould also readily detect transitions associated to the quantum well. These measurements which pave the way to a precise determination of the gap misma tch between the well and the barrier layers are combined with self consiste nt excitonic and envelope function calculations in the context of a model f or the band line-ups which includes the piezoelectric effect. (C) 1999 Else vier Science S.A. All rights reserved.