Analysis and path localization of gate current in AlGaN/GaN HEMTs using low frequency noise measurements and Optical Beam Induced Resistance Change technique

GaN based transistors´ performance and reliability status are largely sensitive to gate conduction mechanisms and surface charges induced by spontaneous and piezoelectric effects. Understanding leakage current origin and kinetic is the key of knowledge for improving GaN technologies. Therefore, room temperature Low Frequency Noise (LFN) and Optical Beam Induced Resistance Change (OBIRCh) measurements have been investigated on the gate current of AlGaN/GaN High Electron Mobility Transistors (HEMTs). LFN measurements are performed under two configurations: the Schottky diode is measured at open drain, and the transistor is investigated in the saturated region (V_DS=8V). On the other hand, the application of the OBIRCh imaging technique is performed on the Schottky diode versus the same gate voltages than for the LFN. This paper focuses on the behavior of the gate-source region of the Schottky diode and on the gate-source and gate-drain regions of the transistor. From the LFN measurements, it is found that the carriers contributing to I_GS are following the same path between gate and source for both configurations (diode, transistor) under elevated reverse gate-source voltage. As from OBIRCh measurements, a spots spread transmit an increase in the current conduction area on the gate width when V_GS decreases (toward high reverse biases). The results allow correlation between these two techniques.