We demonstrate THz intersubband absorption (15.6-26.1 meV) in m-plane AlGaN/GaN quantum wells. We find a trend of decreasing peak energy with increasing quantum well width, in agreement with theoretical expectations. However, a blue-shift of the transition energy of up to 14 meV was observed relative to the calculated values. This blue-shift is shown to decrease with decreasing charge density and is therefore attributed to many-body effects. Furthermore, a ~40% reduction in the linewidth (from roughly 8 to 5 meV) was obtained by reducing the total sheet density and inserting undoped AlGaN layers that separate the wavefunctions from the ionized impurities in the barriers.
@article{arxiv.1406.1772,
title = {Terahertz intersubband absorption in non-polar m-plane AlGaN/GaN quantum wells},
author = {C. Edmunds and J. Shao and M. Shirazi-HD and M. J. Manfra and O. Malis},
journal= {arXiv preprint arXiv:1406.1772},
year = {2015}
}