Optimization of AlGaN films grown by RF atomic nitrogen plasma using in-situ cathodoluminescence

Abstract

In-situ cathodoluminescence (CL) is presented as a technique for determining film composition, optical quality, doping levels, and temperature of MBE grown group III nitride films. Excitation of the films is done with either the Auger or RHEED electron gun operating between 1 and 10 keV. The CL emission is monitored using a 3 nm resolution monochromator. Optimization of the GaN growth process using a RF atomic nitrogen plasma source is discussed using in-situ cathodoluminescence to reduce the yellow defect level present in GaN. Composition and quality of Al x Ga 1-x N films are shown to be quickly determined from the peak position and width. This is extremely useful in the nitride system where reflection high-energy electron diffraction (RHEED) oscillations are not routinely observed. Measurement of the substrate temperature during GaN growth is demonstrated by monitoring the shift in band edge position with temperature. p-type doping and MQW levels observed by CL are shown to allow quick optimization of device and material properties.