Design Space of Delta-Doped β-(Al x Ga1-x )2O3/Ga2O3 High-Electron Mobility Transistors

This work presents a systematic exploration of the design space for delta-doped $\beta $ -(Al _x Ga _1-x ) ₂ O ₃ /Ga _{2} O ₃ high electron mobility transistors (HEMTs) using TCAD simulation. Devices with different delta-doping concentrations, positions, and widths were comprehensively investigated, where the effects of delta-doping properties on device threshold voltages ( ${V}_{\text {TH}}$ ), transconductance, and breakdown voltages (BVs) were elucidated. High delta-doping concentrations resulted in a negative shift in the ${V}_{\text {TH}}$ and an improvement in the transconductance and channel mobility of the devices due to higher concentrations of the two-dimensional electron gas (2DEG) in the channel. However, high delta-doping concentrations degraded the channel quality by inducing a secondary parasitic channel in the delta-doped region, which is ascribed to the severe conduction band bending of the devices. Furthermore, the device BVs were also reduced by high delta-doping concentrations due to the strong electric field crowing effect near the gate edge. Although delta-doping positions closer to the channel improved device performance, caution should be taken to avoid dopant diffusion into the channel, which is detrimental to the electron mobility and transconductance of the devices. In addition, the device ${V}_{\text {TH}}$ varied linearly with the delta-doping width, which can be used to tune the device ${V}_{\text {TH}}$ . Finally, the HEMTs with the gate-recess design were simulated. This work can provide valuable information and crucial guidance for the design and optimization of delta-doped $\beta $ -(Al _x Ga _1-x ) ₂ O ₃ /Ga ₂ O ₃ HEMTs for high-power, high-voltage, and high-frequency electronics.