AlN/GaN Superlattice Channel HEMTs on Silicon Substrate

Abstract

High-electron-mobility transistor (HEMT) with AlN/GaN superlattice (SL) channel has been demonstrated on a silicon substrate. High OFF-state breakdown voltage <inline-formula> <tex-math notation= LaTeX >${V}_{\\text {BR}}$ </tex-math></inline-formula> of 670 V (gate–drain spacing <inline-formula> <tex-math notation= LaTeX >${L}_{\\text {GD}} = 8\\,\\,\\mu \\text{m}$ </tex-math></inline-formula>) along with a maximum output current of 196 mA/mm, a channel electron total mobility of 507 cm²/<inline-formula> <tex-math notation= LaTeX >$\\text{V}\\cdot \\text{s}$ </tex-math></inline-formula>, and an ON/ OFF ratio of over 10⁷ was achieved in this novel HEMT. For the HEMT with <inline-formula> <tex-math notation= LaTeX >${L}_{\\text {GD}} = 22\\,\\,\\mu \\text{m}$ </tex-math></inline-formula>, a high <inline-formula> <tex-math notation= LaTeX >${V}_{\\text {BR}}$ </tex-math></inline-formula> of 1700 V was obtained with substrate floated. The influence of <inline-formula> <tex-math notation= LaTeX >${L}_{\\text {GD}}$ </tex-math></inline-formula>, the gate–source voltage <inline-formula> <tex-math notation= LaTeX >${V}_{\\text {GS}}$ </tex-math></inline-formula>, the isolated pattern, and substrate grounded and floated type was discussed to analyze the breakdown characteristics of HEMT. We investigated the trap states in the AlN/GaN SL channel of HEMTs by frequency-dependent capacitance and conductance measurements. A trap state density of <inline-formula> <tex-math notation= LaTeX >$7.4\\times 10^{{12}}$ </tex-math></inline-formula>–<inline-formula> <tex-math notation= LaTeX >$1.2\\times 10^{{13}}$ </tex-math></inline-formula> cm⁻²eV⁻¹ is located at <inline-formula> <tex-math notation= LaTeX >${E}_{\\text {T}}$ </tex-math></inline-formula> in a range of 0.29–0.33 eV of the main channel, while the trap state density in the parasitic channel decreases from <inline-formula> <tex-math notation= LaTeX >$3.9\\times 10^{{11}}$ </tex-math></inline-formula> cm⁻²eV⁻¹ at an energy of 0.27 eV to <inline-formula> <tex-math notation= LaTeX >$1.1\\times 10^{{11}}$ </tex-math></inline-formula> cm⁻²eV⁻¹ at an energy of 0.38 eV. The fabricated AlN/GaN SL channel HEMTs in this work reveal a great step toward the realization of the SL channel HEMTs on cost-effective silicon substrate and provide a novel technology for AlGaN multichannel devices to obtain high output current.