Depth-resolved cathodoluminescence of III-V nitride films grown by plasma-assisted molecular beam epitaxy

The luminescence properties of III-V nitride films (an undoped GaN, an undoped GaN/Al_0.2Ga_0.8N multiquantum well, and a p-type Mg-doped GaN films) were investigated using the depth-resolved cathodoluminescence (CL) spectroscopy. From the low- and room-temperature CL of the undoped GaN and GaN/AlGaN MQW films, an emission at 2.9eV was found with the longer penetration depth and is attributed to the higher density of dislocations at the interface between the film and the substrate. In order to explain the depth-resolved CL of the Mg-doped GaN film, the configuration coordinate model is proposed on the basis of the local strain near the Mg impurities. This model demonstrates that local strain may play a crucial role in controlling the radiative efficiency, line width, and peak position of the luminescence from the film.