GaN HEMT Thermal Characteristics Evaluation Using an Integrated Approach Based on the Combined Use of First-Principles and Device Simulations

The GaN high electron mobility transistor (HEMT) thermal characteristics were evaluated employing an integrated approach based on the combined use of ab initio (first-principles) and device simulations. The necessity of utilizing such a method arises when model parameters required for device simulation are unavailable or not suited to certain conditions. A fine example is thermal conductivity of crystalline materials, which is strongly dependent on the defect density, isotopic purity and temperature. Since the developed temperature due to self-heating is highly sensitive to the thermal conductivities of certain regions of the device structure, it is of great importance to use correct thermal conductivity models that are incorporated into the heat flow equation. A combination of ab initio calculations and solutions of the linearized phonon Boltzmann transport equation is a high-end tool to estimate the thermal properties of crystalline materials. In this paper, firstly, the values of the thermal conductivity and thermal capacity of AlN, GaN, Al0.21Ga0.79N and Al0.5Ga0.5N were calculated in the range of temperature from 20 K to 1000 K. Secondly, device simulation of a GaN HEMT was performed and the thermal characteristics were evaluated.