IV, noise and electroluminescence analysis of stress-induced percolation paths in AlGaN/GaN high electron mobility transistors

Properties of stress-induced percolation paths in AlGaN in step-stressed AlGaN/GaN high electron mobility transistors are investigated in details. DC and transient gate and drain current analysis are combined with low frequency noise and electroluminescence measurements. The observation of random telegraph signal (RTS) noise with large relative amplitude indicates that RTS is due to modulation of gate current in the percolation path by action of single defects. Measurements of RTS amplitude as a function of forward or reverse gate voltage can reveal masked gate leakage current components related to individual percolation paths. The observed gradual increase in forward gate current ideality factor with progressing stress, indicating defect penetration inside the percolation path in AlGaN, is explained by a simple model. The role of slow trapping in the modulation of current in the percolation path is discussed too.