Crystal orientation effects on the optical properties of wurtzite GaN/AlN quantum dots on semi-polar substrates

Optical properties of epitaxial quantum dots are of considerable interest for high efficiency opto-electronic devices and room-temperature quantum light sources. In this work, the general crystal orientation effects on the spontaneous emission peak of wurtzite (WZ) GaN/AlN quantum dots (QDs) grown on semi-polar substrates is studied theoretically. As crystal orientation changes from Θ=0° to Θ=90°, the spontaneous emission peak is predicted to increase almost ten-fold. This drastic change of the spontaneous emission peak is caused by the rapid increase of the optical dipole matrix elements with crystal orientation angle. The change of the optical matrix element is due to the change of the screening of built-in potential of the WZ QDs with the crystal orientation change. In particular, the spontaneous emission peak rapidly increases when the crystal angle exceeds Θ=50°.