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

Abstract

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 $(\mathrm{E}_{\mathrm{G}} > 3.4\mathrm{eV})$ . 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 $\mathrm{p}-\mathrm{Al}_{0.3}\mathrm{Ga}_{0.7}\mathrm{N}$ 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 $(> 60\mathrm{mA}/\mathrm{mm})$ , no gate hysteresis $(\Delta \mathrm{V} , and exceptionally low gate leakage current of $ even under high forward bias of $\mathrm{V}_{\mathrm{GS}}=8\mathrm{V}$ .