The Impacts of Different Electrode Structures on the Device Performance of β-(Al x Ga1−x )2O3/Ga2O3 Heterostructure Metal–Semiconductor–Metal Photodetectors

The effects of different electrode structures on the device performance of $\beta $ -(Al $_{\textit{x}}$ Ga $_{\text{1$ - $} \textit{x}}\text{)}_{\text{2}}$ O $_{\text{3}}$ /Ga $_{\text{2}}$ O $_{\text{3}}$ heterostructure metal–semiconductor–metal photodetectors (MSM PDs) have been investigated via the 2-D numerical simulation, which was developed on the basis of the modified continuity equation, transport equation, and Poisson equation. Numerical simulations were performed on the planar-type $\beta $ -Ga $_{\text{2}}$ O $_{\text{3}}$ , $\beta $ -(Al $_{\textit{x}}$ Ga $_{\text{1$ - $} \textit{x}}\text{)}_{\text{2}}$ O $_{\text{3}}$ , MgZnO/ZnO, and $\beta $ -(Al $_{\textit{x}}$ Ga $_{\text{1$ - $} \textit{x}}\text{)}_{\text{2}}$ O $_{\text{3}}$ /Ga $_{\text{2}}$ O $_{\text{3}}$ MSM PDs and anode recessed InGaN/GaN MSM PD and compared with the corresponding experimental data so as to confirm the correctness of our model. Then, the current–voltage, responsivity, and detectivity characteristics of the $\beta $ -(Al $_{\textit{x}}$ Ga $_{\text{1$ - $} \textit{x}}\text{)}_{\text{2}}$ O $_{\text{3}}$ /Ga $_{\text{2}}$ O $_{\text{3}}$ heterostructure MSM PDs with different electrode structures, such as planar electrodes, recessed anodes, and recessed anodes and cathodes, were numerically calculated and analyzed for symmetric/asymmetric electrode materials and widths. Results showed that the recessed electrode structures could effectively enhance the photocurrents of proposed devices without significantly increasing the dark currents, and the photo-dark current ratios of recessed-type $\beta $ -(Al $_{\textit{x}}$ Ga $_{\text{1$ - $} \textit{x}}\text{)}_{\text{2}}$ O $_{\text{3}}$ /Ga $_{\text{2}}$ O $_{\text{3}}$ PDs could be up to 10 $^\text{5}$ . It was also noted that the recessed-type $\beta $ -(Al $_{\textit{x}}$ Ga $_{\text{1$ - $} \textit{x}}\text{)}_{\text{2}}$ O $_{\text{3}}$ /Ga $_{\text{2}}$ O $_{\text{3}}$ PDs with asymmetric electrode materials exhibit exceptionally high detectivity of over 10 $^{\text{17}}$ Jones. This work would benefit the research and development of $\beta $ -(Al $_{\textit{x}}$ Ga $_{\text{1$ - $} \textit{x}}\text{)}_{\text{2}}$ O $_{\text{3}}$ /Ga $_{\text{2}}$ O $_{\text{3}}$ heterostructure MSM PDs.