Effects of Self-Heating on Performance Degradation in AlGaN/GaN-Based Devices

A self-consistent electrothermal transport model that couples electrical and thermal transport equations is established and applied to AlGaN/GaN device structures grown on the following three different substrate materials: 1) SiC; 2) Si; and 3)sapphire. Both the resultantI-Vcharacteristics and surface temperatures are compared to experimentalI-Vmeasurements and Raman spectroscopy temperature measurements. The very consistent agreement between measurements and simulations confirms the validity of the model and its numerical rendition. The results explain why the current saturation in measuredI-Vcharacteristics occurs at a much lower electric field than that for the saturation of electron drift velocity. The marked difference in saturated current levels for AlGaN/GaN structures on SiC, Si, andsapphiresubstrates is directly related to the different self-heating levels that resulted from the different biasing conditions and the distinctive substrate materials.