Near-infrared intersubband absorption in GaN/AlN quantum wells grown by molecular beam epitaxy

GaN/AlN multiple-quantum-well structures were grown by molecular beam epitaxy. Abrupt interfaces and good periodicity were confirmed. Absorption measurements indicated that intersubband absorptions occurred at wavelengths of 1.3-2.2 mum. Spectral fits by Lorentzians suggested that the well thicknesses fluctuated by two monolayers. The linewidths of the individual fits were as narrow as 80-120 meV. The characteristics of the absorption saturation were investigated at a wavelength of 1.46 mum. A relaxation time of 400 fs and saturation energy density of 0.5 pJ/mum2 were obtained. These results are promising for realizing ultrafast optical switches with energy consumption of the picojoule order. (C) 2002 American Institute of Physics.