Maximum, effective, and average thermal resistance for GaN-based HEMTs on SiC, Si and sapphire substrates

Abstract

The maximum, effective, and average thermal resistance (R_TH) of AlGaN/GaN and InAlN/GaN high-electron mobility transistors (HEMTs) on silicon carbide (SiC), silicon (Si), and sapphire substrates are reported using TCAD simulation. After validating simulated I-V properties, R_TH is deduced from self-heating (SH)-induced rise in channel temperature (ΔT) versus dissipated power (P_D) plot. The maximum thermal resistance (R_THmax) determines HEMT reliability at higher power dissipation; so, peak channel temperature (T_max) is extracted. The simulated ΔT_max-P_D plots are compared with the literature results for each HEMT structure. The estimated R_THmax is consistent with the reported experimental values, verifying the TCAD model and confirming the validity of reported R_TH values. The effective thermal resistance (R_THeff) is needed to simulate the electrical properties using the compact model. For this purpose, isothermal I_DS-V_DS simulations are carried out at different temperatures without SH effects. Then, the cross-over temperature points (ΔT_eff) are identified by evaluating the isothermal data with the actual output properties at a particular P_D. The average thermal resistance (R_THavg) of the HEMT is computed by averaging the lattice temperature profile along the channel (mean channel temperature), and R_THavg is compared with R_THeff.