Improvement of near-infrared absorption linewidth in AlGaN/GaN superlattices by optimization of delta-doping location

We report a systematic study of the near-infrared intersubband absorption in AlGaN/GaN superlattices grown by plasma-assisted molecular-beam epitaxy as a function of Si-doping profile with and without delta-doping. The transition energies are in agreement with theoretical calculations including many-body effects. A dramatic reduction of the intersubband absorption linewidth is observed when the delta-doping is placed at the end of the quantum well. This reduction is attributed to the improvement of interface roughness. The linewidth dependence on interface roughness is well reproduced by a model that considers the distribution of well widths measured with transmission electron microscopy. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751040]