Intersubband transitions in Si-doped molecular beam epitaxy grown GaN/AlGaN multiple quantum wells on c-plane sapphire were investigated using the Fourier-transform infrared optical absorption technique. Several GaN quantum well samples were grown with either AlGaN bulk or GaN/AlGaN short period superlattice barriers. The measurements were made in a waveguide configuration utilizing a facet polished at 45degrees to the c plane. The integrated area of the intersubband transitions in several waveguides cut from different location of the wafer was measured, from which we estimated the two-dimensional electron gas density (sigma). The measured values of sigma are about two orders of magnitude larger than the Si doping level of similar to8x10(17) cm(-3), which is consistent with the polarization effects, particularly considering the large number of GaN/AlGaN interfaces. The internal quantum efficiency of the intersubband transitions was estimated to be on the order of 40 for samples with superlattice barriers. (C) 2003 American Institute of Physics. References: 23
展开▼
