Abstract We report RF small signal analysis of ultra-wide bandgap AlGaN channel MESFETs with Al composition of 70%. Ohmic contacts are achieved using a linearly-graded and heavily-doped AlGaN layer grown by metal organic chemical vapor deposition. The device with a gate length of 250 nm shows a drain current density (IDSS) of 370 mA/mm when the gate is shorted to source, unity current gain cutoff frequency (fT) of 8.8 GHz, and maximum oscillating frequency (fMAX) of 15 GHz. Bias-dependent device parameters are extracted from measured S-parameters based on a small-signal equivalent circuit model. The peak effective electron velocity of 2.9 × 106 cm/s is obtained at VGS = − 7 V. We show that the average electron velocity (ve) under the gate limits the device intrinsic RF performance while the high source access resistance (Rs) and drain access resistance (Rd) limits the device extrinsic RF performance.

中文翻译：

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超宽带隙 Al0.7Ga0.3N 沟道 MESFET 的小信号分析

摘要 我们报告了铝成分为 70% 的超宽带隙 AlGaN 通道 MESFET 的 RF 小信号分析。欧姆接触是使用通过金属有机化学气相沉积生长的线性渐变和重掺杂 AlGaN 层实现的。栅极长度为 250 nm 的器件在栅极与源极短路时的漏极电流密度 (IDSS) 为 370 mA/mm，单位电流增益截止频率 (fT) 为 8.8 GHz，最大振荡频率 (fMAX) 为15 GHz。基于小信号等效电路模型从测量的 S 参数中提取与偏置相关的器件参数。在 VGS = − 7 V 时获得 2.9 × 106 cm/s 的峰值有效电子速度。