Study On High-Electric-Field Degradation Effects And Temperature Characteristics Of AlGaN/GaN HEMTs

AlGaN/GaN high-electron-mobility transistors (HEMTs) are of much interest for microwave power and high-temperature applications because of the high break-down field and high electronic velocities in group-III nitride alloy semiconductors.However, the reliability problem is one of the issues that remain to be solved in order to move toward commercially available devices.Research on the high-field stress reliability and temperature characteristics of AlGaN/GaN HEMTs are carried out extensively in this paper. Major research work and results are as follows:Firstly, a complete set of AlGaN/GaN HEMT process flow is given and AlGaN/GaN HEMTs with good performance are produced on sapphire and SiC substrate;Secondly, the high-field stress degradation behaviors of GaN-based device are analyzed. Device degradation effects under several typical stress conditions are studied in particular, and then, the degradation rule of the device parameters with stress time is obtained. The effect of stress condition on device degradation is studied through variable gate voltage stress and variable drain voltage stress methods. The results show that the degradation mechanism differs at different stress condition. Under on-state condition, CHC effect is the dominant effect, while GEI effect under off-state condition. In addition, several measures are proposed to improve the reliability of HEMTs;Finally, temperature characteristics and thermal storage characteristics of self-developed AlGaN/GaN HEMTs are studied, the results show that the performance degradation under high temperature is mainly due to the degradation of mobility, while the device performance improvement after short-term heat storage is caused by the release of electrons from AlGaN/GaN traps.In summary, well characterized AlGaN/GaN HEMTs are successfully developed through a series of process steps in this paper, and satisfactory results are finally obtained through the analysis of high-field stress reliability and temperature characteristics of the device.