The development of processes for epitaxial growth of vertical gallium nitride (GaN) drift layers enabling 1.2 kV breakdown voltage on low‐cost sapphire substrates is presented in comparison to GaN bulk substrates. The targeted blocking capability demands drift layers with a thickness of 10 μm and low but controllable n‐type doping. Using a growth rate of 2.5 μm h−1 the concentration of unintentionally incorporated carbon is sufficiently low to adjust the n‐type carrier concentration to ≈1 × 1016 cm−3 for all types of substrates. To assess GaN drift region properties in terms of forward bias conductivity and reverse bias blocking strength, a quasi‐vertical p‐n‐diode structure is utilized. Bow reduction of GaN‐on‐sapphire structures is achieved using a stealth laser scribing process. Breakdown voltages higher than 1600 V and a specific on‐state resistance as low as 0.7 mΩ cm2 are obtained with diodes fabricated on GaN substrates. Similar structures grown on sapphire show breakdown voltages of about 1300 V due to higher levels of current leakage. Comparing different types of substrates, a direct correlation between dislocation density in the drift layer with the leakage current in p‐n diodes is deduced.

中文翻译：

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用于 1.2 kV 级垂直功率器件的蓝宝石和 GaN 衬底上的 GaN 漂移层

与 GaN 块状衬底相比，介绍了垂直氮化镓 (GaN) 漂移层外延生长工艺的开发，可在低成本蓝宝石衬底上实现 1.2 kV 击穿电压。目标阻挡能力需要厚度为 10 μm 的漂移层和低但可控的 n 型掺杂。使用 2.5 μm h 的生长速率−1无意掺入的碳浓度足够低，可将 n 型载流子浓度调整至 ≈1 × 1016厘米−3适用于所有类型的基材。为了评估 GaN 漂移区在正向偏压电导率和反向偏压阻断强度方面的特性，采用了准垂直 p-n 二极管结构。蓝宝石基氮化镓结构的弓形减小是通过隐形激光划片工艺实现的。击穿电压高于 1600 V，比通态电阻低至 0.7 mΩ cm2是用在 GaN 衬底上制造的二极管获得的。由于漏电流较高，在蓝宝石上生长的类似结构显示出约 1300 V 的击穿电压。比较不同类型的衬底，推断出漂移层中的位错密度与 p-n 二极管中的漏电流之间的直接相关性。