New developments for nitride unipolar devices at 1.3-1.5 μm wavelengths

We present a systematic investigation of ultrathin single and coupled GaN/AlN quantum wells grown by molecular beam epitaxy for applications to unipolar devices. Narrow Lorentzian-shaped intersubband absorptions are demonstrated tunable at telecommunication wavelengths. The linewidth is as small as 40 meV which sets a new state-of-the-art. Simulation of the intersubband wavelength and comparison with measurements leads us to revise the value of the conduction band offset at the GaN/AlN interface (1.7 +/- 0.05 eV). We also present the observation of strong electron state coupling between two GaN wells separated by an ultra-thin 2 monolayer thick AlN barrier. This study allows us to refine the potential description at the GaN/AlN interface at the atomic monolayer scale. Excellent agreement with measurements is achieved assuming a potential drop over 1 ML. (c) 2006 Elsevier Ltd. All rights reserved.