This article reports on the experimental and analytical determination of the optimum carbon concentration in GaN to achieve enhanced breakdown in AlGaN/GaN high-electron mobility transistors (HEMTs). The lateral breakdown voltage increases when carbon doping is increased from 3×10183\times 10^{{18}} to 1019 cm−3 beyond which it decreases, whereas there is no substantial enhancement in the vertical breakdown voltage with carbon doping. We invoke carrier statistics in a compensated semiconductor vis-à-vis the formation energy of carbon-occupying Ga (or N) vacancies to explain the observed buffer leakage. Temperature-dependent data indicate that the buffer leakage current is due to hopping transport, the activation energy of which yields the positions of the defect states within the bandgap. The increase in buffer leakage beyond optimum C concentration is attributed to the formation of shallow donor traps by carbon atoms occupying Ga vacancies (CGa). The observations correlated with the relative intensities of the defect-mediated peaks in the cathodoluminescence (CL) data of the samples. Based on our findings, a C doping beyond 1019 cm−3 is not recommended for GaN buffers in order to achieve high breakdown voltages.

中文翻译：

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硅基 GaN 中的最佳碳浓度可增强 AlGaN/GaN HEMT 的击穿能力


本文报告了通过实验和分析确定 GaN 中最佳碳浓度的方法，以实现 AlGaN/GaN 高电子迁移率晶体管 (HEMT) 的增强击穿。当碳掺杂从3×10183×10^{{18}}增加到1019 cm−3时，横向击穿电压增加，超过1019 cm−3则横向击穿电压下降，而碳掺杂的垂直击穿电压没有实质性增强。我们引用补偿半导体中相对于碳占据的 Ga（或 N）空位的形成能的载流子统计数据来解释观察到的缓冲器泄漏。与温度相关的数据表明，缓冲器漏电流是由于跳跃传输引起的，其激活能产生带隙内缺陷态的位置。缓冲泄漏的增加超过最佳 C 浓度是由于碳原子占据 Ga 空位 (CGa) 形成浅施主陷阱。观察结果与样品阴极发光 (CL) 数据中缺陷介导峰的相对强度相关。根据我们的发现，为了实现高击穿电压，不建议 GaN 缓冲器使用超过 1019 cm−3 的 C 掺杂。