Extraction of Bias-dependent Source and Drain Resistances in AlGaN/GaN MIS-HEMTs Using Pulsed Measurement Method

A new method for extraction of bias-dependent source and drain resistances in AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) is reported. The total source/drain access resistances are extracted by measuring the pulsed transfer characteristics of test devices with various quiescent biases. With short pulse width, the charge trapping and thermal effects will not be affected by the magnitude of pulse voltages, and thus the extracted resistances correspond to the quiescent bias condition. As a result, the dependences of total access resistances on the gate and drain voltages are obtained. While employing the dual-sweep combinational transconductance technique, the source and drain resistances are separated further. To investigate the variation of access resistances with applied voltages, AlGaN/GaN HEMTs are also illuminated with a 365-nm ultraviolet (UV) source during pulsed measurements. Under UV illumination, the resistance will be less dependent on the drain voltage, indicating the charge trapping in GaN buffer layer has a large impact on the access resistance.