Optimization for the growth condition of In-situ SiNx cap layer on ultrathin barrier InAlGaN/GaN heterostructures by Metal-Organic Chemical Vapor Deposition

We investigate the dependence of material and electrical properties on the growth temperature of In-situ SiNx on InAlGaN/GaN heterostructures grown by Metal-Organic Chemical Vapor Deposition. Degradation of the interface between SiNx and InAlGaN layer was observed when growth temperature is below 900 ℃ or above 1100 ℃. With the optimized SiNx growth temperature, the high-quality SiNx and low interface trap density can be realized. Thus, the double-sweep capacitance-voltage measurement showed a sharp transition from charge accumulation to depletion with low hysteresis of 0.09 V. A small threshold-voltage shift after gate bias stress (1001 s) was also characterized by I-V measurement.