Growth and Characterization of GaN/AlGaN Superlattices for Near-Infrared Intersubband Transitions

We report the results of the growth by molecular beam epitaxy of GaN/Al_xGa_1—xN superlattice (SL) structures with single or double quantum wells and thick Al_xGa_1—xN or short-period SL barriers. The dependence of intersubband absorption on the well width for single well SL structures was systematically investigated. For GaN quantum wells interleaved with SL barriers, the upper state electron confinement was maintained by Bragg reflection from the minigaps formed within the barriers. In addition, evidence of electron transfer from doped SL barriers to undoped GaN quantum wells was obtained. Abrupt interfaces and coherent periodicities of the SL structures were confirmed by transmission electron microscopy and X-ray diffraction measurements. Intersubband absorption at peak wavelengths between 1.4 and 4.2 μm has been observed.