PDI has recently opened a new application laboratory for time-resolved cathodoluminescence (TRCL) spectroscopy, which combines high spatial, spectral, and temporal resolution to investigate the dynamics of charge carriers in semiconductors,
with a particular focus on optimized deep ultraviolet (UV) detection. This unique experimental facility is part of the analytical scanning electron microscopy (SEM) group in the semiconductor spectroscopy department. First investigations have provided new insights into the spectral features of the ultrawide bandgap semiconductor AlN, as well as into the role of point defects in polar c-plane quantum wells for deep UV light-emitting devices (LEDs). The current project would expand these spectroscopic investigations to the nonpolar m-plane growth direction of AlN and (Al, Ga)N heterostructures. On the one hand, measurements in this geometry would allow us to investigate the importance of light extraction efficiency linked to the valence band symmetries in high Al content alloys. On the other hand, the polar wurtzite crystal structure induces strong polarization fields across heterostructures that strongly influence device characteristics, but are absent for nonpolar growth. Dedicated samples for this study will be grown at PDI by molecular beam epitaxy.