Performance Improvement of AlN–GaN-Based Intersubband Detectors by Using Quantum Dots

We report a strong performance improvement for 1.55-
$\mu$
m AlN–GaN-based intersubband photodetectors. Thanks to the use of quantum dots (QDs) instead of quantum wells (QWs), a factor of 60 could be gained in terms of maximum responsivity. In addition, this performance was achieved at a considerably higher temperature of 160 K instead of 80 K as typically seen for QWs. The responsivity of these photodetectors, which are based on optical rectification, is strongly influenced by their excited state lifetime. We believe that a much longer electron lifetime in the upper QD states and an increased lateral electron displacement are responsible for the observed improvement.