## 3 Results
### Influence of Doping Concentration and Thickness of p-SnO CBL  
In this section, the effects of p-type doping concentration and thickness of p-SnO CBL on the basic characteristics of device are systematically studied. As shown in Figure 4a,b, when the thickness of p-SnO CBL was set to 0.8 um and the p-type doping concentration increased from \(2\times 10^{17}\) cm\({}^{-3}\) to \(2\times 10^{18}\) cm\({}^{-3}\), the breakdown voltage of Ga\({}_{2}\)O\({}_{3}\) MOSFET with a p-SnO CBL can be in the range from 361 V (corresponding to \(2\times 10^{18}\) cm\({}^{-3}\) doping concentration) to 518 V (corresponding to \(2\times 10^{17}\) cm\({}^{-3}\) doping concentration), and the threshold voltage was in the range of 2.4-2.8 V. As shown in Figure 4c, the breakdown voltage of the vertical MOSFET with p-SnO CBL has a peak value. When the thickness of CBL was about 0.8 um, the breakdown voltage of the device reached a peak value of 518 V. When the thickness of CBL increased or decreased, the breakdown voltage decreased correspondingly, and the threshold voltage range of the device was small, which was 2.4-2.8 V. By adjusting the p-type doping concentration and thickness of p-SnO CBL, the breakdown voltage of the device can be greatly increased and the threshold voltage of the device can be adjusted in a small range to improve the performance of the device, which is conducive to the preparation of power devices. To better understand the physical mechanism of p-type doping concentration and thickness of p-SnO CBL on the device, the energy band diagrams of CBL with different p-type doping concentration and thickness are extracted in Figure 5a. As shown in Figure 5a, the higher the p-type doping concentration of CBL, the higher the potential barrier in the channel region. To achieve the low barrier conduction state, a higher gate voltage is required so that the threshold voltage of the device is increased. In Figure 5a, the thickness of p-SnO CBL hardly affects the height of channel barrier, so the threshold voltage of the device hardly changes. As for the breakdown voltage, it can be seen from Figure 5b that the lower the p-type doping concentration of CBL, the thicker the depletion layer thickness of the drift layer of the device, causing an increase in the breakdown voltage. To see the relationship between CBL thickness and depletion layer more intuitively, the parameter was directly extracted from the simulation results and a curve was drawn, shown in Figure 5c. With the increase in CBL thickness, the effective depletion layer thickness increased and the breakdown voltage increased. Until the CBL thickness reached 0.8 um, the effective depletion layer thickness decreased and the breakdown voltage decreased. Additionally, that is consistent with the previous trend of breakdown voltage. As seen from the above Formula (1), when the doping concentration and material remained unchanged, the thickness of the depletion layer mainly depended on the applied voltage. The CBL was thin and the device broke down, as seen from the left side of Figure 5d. At this time, there was a certain concentration of electrons in the CBL, indicating that part of the current flowed directly from the CBL. Additionally, the CBL lost the function of blocking the current, so the breakdown voltage of the device decreased and the thickness of the depletion layer decreased similarly. When the thickness of CBL increased, as shown on the right side of Figure 5d, the current in the CBL layer gradually decreased to 0. At this time, the breakdown voltage increased and the thickness of the depletion layer showed an upward trend. As can be seen from Figure 5e, with the increase in the thickness of the  
Figure 4: (**a**) The breakdown voltage, (**b**) the threshold voltage curves under different doping concentrations obtained when the thickness of CBL was 0.8 μm, and (**c**) the doping concentration of CBL at 2 \(\times\) 10\({}^{17}\) cm\({}^{-3}\), with the breakdown voltage and threshold voltage curves of the device obtained at different thickness.