Impact of pulse operation conditions on the transient temperature distribution of GaN HEMTs via Raman thermometry operando analysis

High performance GaN based power devices operating at high frequencies are required in the fields of energy conversion, communication and aerospace applications. However, heat dissipation has become a major challenge that limits the further improvement of device performance. Investigating and understanding the transient thermal response of power devices under operando conditions are of great importance in thermal management whereas such studies are quite limited. We report in this work the in situ operando analysis of the transient temperature profile of GaN multi-finger high electron mobility transistors (HEMTs). The variation of the transient channel temperature profile of the GaN HEMT with the frequency and duty cycle of electrical pulses was thoroughly investigated. It was found that the duty cycle has a significant impact on the maximum temperature, and the maximum temperature augmented 2.5 times from 102 °C to 256 °C as the duty cycle increased from 10% to 50%. A small duty cycle (<30%) is necessary to maintain a safe temperature of the device. We further demonstrate that the channel temperature of the device in the off state cannot be completely reduced to room temperature due to heat accumulation. The finite element analysis confirms the heat accumulation and thus explains the experimental results well. These results not only lay the solid and reliable experimental and methodological groundwork to understand and improve the transient thermal response and heat dissipation of GaN HEMTs, but also provide a potential universal approach for enhancing the thermal design and achieving high performance power devices.