Terahertz intersubband absorption in non-polar m-plane AlGaN/GaN quantum wells

TL;DR

This paper reports on the observation of terahertz intersubband absorption in m-plane AlGaN/GaN quantum wells, highlighting the effects of well width, charge density, and impurity separation on transition energies and linewidths.

Contribution

It provides experimental evidence of THz intersubband absorption in non-polar m-plane AlGaN/GaN quantum wells and investigates many-body effects and linewidth reduction strategies.

Findings

Decreasing peak energy with increasing well width matches theory.

Observed blue-shift of up to 14 meV due to many-body effects.

Linewidth reduced by ~40% through density control and impurity separation.

Abstract

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.