Control of Yellow Photoluminescence in AlGaN/GaN Heterostructures

Photoluminescence with the peak corresponding to yellow light in the visible spectrum (the so−called yellow luminescence) is generated by deep levels in the buffer GaN layer of the ehterostructures and depeonds on heterostructure growth conditions. In turn, the deep levels affect the resistivity of the ohimic contacts of RF transistors based on these heterostructures. This determines the reliability of GaN HF transistor operation. Two types of instruments have been developed for controlling photoluminescence with the peak in the yellow spectral region for characterizing the quality of AlGaN/GaN/SiC and AlGaN/GaN/Al2O3 heterostructures. One of them provides for rapid control of yellow photoluminescence and the other allows mapping of photoluminescence across the heterostructure area. Examples of photoluminescence maps for experimental structures grown on different substrates have been given.