Electro-Thermal Simulation of Delta-Doped $\boldsymbol{\beta}$ -Ga 2 O 3 Field Effect Transistors

Gallium oxide has potential to emerge as a better alternative to wide bandgap materials such as GaN, SiC etc. for radio frequency and power electronics applications. It can achieve higher breakdown voltage and efficiency than GaN and SiC due to its significantly higher bandgap and Baliga's figure of merit. In this work, we have studied electrical and thermal characteristics of a delta-doped $\beta$ -Ga 2 O 3 Field Effect Transistor (FET). In this FET, a thin layer of Ga 2 O 3 is grown epitaxially on Fe doped semi-insulating Ga 2 O 3 substrate; all grown in (010) direction. First, a 2-D electro-thermal model is developed and numerically computed electrical characteristics are matched with the measurements. The Thermodynamic model in Sentaurus TCAD is used for these numerical simulations. Temperature profile and location of hot-spot in the device were determined. The maximum drain current of 154.4 mA/mm of channel width was predicted at drain-source voltage of 10 V and gate-source voltage of 2 V. The peak temperature of device computed using 2-D model is 475 K at this biased voltage just below the gate edge that is near the drain side. Second, a 3-D model was used to predict peak temperature more accurately. 3-D model predicts peak temperature at the specified bias condition to be 416 K. Thus, we highlighted that 2-D model over-predicts peak temperature. Finally, we explored two different passive cooling mechanisms– (1) replacement of substrate with a higher thermal conductivity substrate and (2) addition of a passivation layer on top of the semiconducting Ga 2 O 3 layer. First method is observed to be more effective in reducing the peak and overall temperature in the device.