AlN/GaN Superlattice Channel HEMTs on Silicon Substrate

High-electron-mobility transistor (HEMT) with AlN/GaN superlattice (SL) channel has been demonstrated on a silicon substrate. High OFF-state breakdown voltage ${V}_{\text {BR}}$ of 670 V (gate–drain spacing ${L}_{\text {GD}} = 8\,\,\mu \text{m}$ ) along with a maximum output current of 196 mA/mm, a channel electron total mobility of 507 cm2/ $\text{V}\cdot \text{s}$ , and an ON/ OFF ratio of over 107 was achieved in this novel HEMT. For the HEMT with ${L}_{\text {GD}} = 22\,\,\mu \text{m}$ , a high ${V}_{\text {BR}}$ of 1700 V was obtained with substrate floated. The influence of ${L}_{\text {GD}}$ , the gate–source voltage ${V}_{\text {GS}}$ , 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 $7.4\times 10^{{12}}$ – $1.2\times 10^{{13}}$ cm−2eV−1 is located at ${E}_{\text {T}}$ in a range of 0.29–0.33 eV of the main channel, while the trap state density in the parasitic channel decreases from $3.9\times 10^{{11}}$ cm−2eV−1 at an energy of 0.27 eV to $1.1\times 10^{{11}}$ 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.