The ultra-wide bandgap of Al-rich AlGaN is expected to support a significantly larger breakdown field compared to GaN, but the reported performance thus far has been limited by the use of foreign substrates. In this Letter, the material and electrical properties of Al0.85Ga0.15N/Al0.6Ga0.4N high electron mobility transistors (HEMT) grown on a 2-in. single crystal AlN substrate are investigated, and it is demonstrated that native AlN substrates unlock the potential for Al-rich AlGaN to sustain large fields in such devices. We further study how Ohmic contacts made directly to a Si-doped channel layer reduce the knee voltage and increase the output current density. High-quality AlGaN growth is confirmed via scanning transmission electron microscopy, which also reveals the absence of metal penetration at the Ohmic contact interface and is in contrast to established GaN HEMT technology. Two-terminal mesa breakdown characteristics with 1.3 μm separation possess a record-high breakdown field strength of ∼11.5 MV/cm for an undoped Al0.6Ga0.4N-channel layer. The breakdown voltages for three-terminal devices measured with gate-drain distances of 4 and 9 μm are 850 and 1500 V, respectively.

中文翻译：

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在原生 AlN 基板上的 Al0.85Ga0.15N/Al0.6Ga0.4N 高电子迁移率晶体管中记录 >10 MV/cm 台面击穿场

与 GaN 相比，富含 Al 的 AlGaN 的超宽带隙有望支持更大的击穿场，但迄今为止报道的性能受到国外衬底使用的限制。在这封信中，Al0.85Ga0.15N/Al0.6Ga0.4N 高电子迁移率晶体管 (HEMT) 的材料和电学特性在 2 英寸生长。对单晶 AlN 衬底进行了研究，结果表明，原生 AlN 衬底释放了富含 Al 的 AlGaN 在此类设备中维持大场强的潜力。我们进一步研究了直接与硅掺杂沟道层形成的欧姆接触如何降低拐点电压并增加输出电流密度。通过扫描透射电子显微镜确认高质量的 AlGaN 生长，这也揭示了欧姆接触界面没有金属渗透，这与已建立的 GaN HEMT 技术形成对比。对于未掺杂的 Al0.6Ga0.4N 沟道层，具有 1.3 μm 间距的两端台面击穿特性具有 ~11.5 MV/cm 的创纪录击穿场强。栅极-漏极距离为 4 μm 和 9 μm 时测得的三端子器件的击穿电压分别为 850 和 1500 V。