Effects of a SiN_x capping layer on the properties of GaN treated by rapid thermal annealing

The effects of rapid thermal annealing (RTA) on GaN films capped with SiNs layers were investigated. After RTA, GaN films capped with SiN_x were compared with GaN films without the SiN_x layer. Hall measurements, double-crystal X-ray diffraction (DCXRD), Raman spectroscopy, and photoluminescence (PL) were used to monitor the changes in the electrical, the structural, and the optical properties. The carrier concentration of the GaN films with the SiNs capping layers decreased and the carrier mobility increased, compared to those of GaN films without the SiN_x capping layers. After RTA, the results of Raman spectra and DCXRD improved. It can be assumed that stress was relaxed and the crystalline quality improved by the annealing process. Also, the results for the GaN epilayers capped with SiNs improved more than the results for the GaN epilayers without SiN_x. From these results, it can be concluded that the SiN_x cap layer plays an important role in preventing GaN decomposition.