Enhancement-mode Al0$_{\mathbf{45}}\mathbf{Ga}_{\mathbf{0.55}}\mathbf{N}/\mathbf{Al}_{\mathbf{0.3}}\mathbf{Ga}_{\mathbf{0.7}}\mathbf{N}$ High Electron Mobility Transistor with p- $\mathbf{Al}_{\mathbf{0.3}}\mathbf{Ga}_{\mathbf{0.7}}\mathbf{N}$ Gate

High aluminum content AIGaN channel high electron mobility transistors (HEMTs) are an attractive candidate for the next generation of RF and high-power applications amongst ultra-wide bandgap materials. This is due to numerous beneficial intrinsic material properties, such as high saturation velocity and large critical electric field. The built-in polarization electric field populates the 2-dimensional electron gas (2DEG) which cannot be depleted entirely at zero bias by the Schottky contact for a reasonable barrier thickness. As was observed in GaN channel HEMTs, these AIGaN channel devices intrinsically operate as depletion mode (d-mode). While d-mode devices are preferable for RF applications, high power applications typically require enhancement mode (e-mode) operation in order to guarantee system reliability [1]. Through the use of a p-Al
_0.3
Ga
_0.7
N gate on an AIGaN channel HEMT, this work shows the capability to achieve enhancement-mode operation with a +0.3V threshold voltage, high saturated drain current, no gate hysteresis, and exceptionally low gate leakage current of even under high forward bias of VGS=8V.