We investigated the impact of selective thermal etching in a mixed hydrogen and ammonia atmosphere on the crystal quality and electrical characteristics of Ga- and N-polar AlGaN/GaN heterostructures. It was revealed that the etching rate of N-polar GaN is lower than that of Ga-polar GaN under our experimental conditions, and they showed a similar dependence on process temperature with almost the same activation energies. We demonstrated the use of a thin AlGaN layer as a selective etching stopper for both Ga- and N-polarity. The AlGaN stoppers exhibited a smooth surface after etching the GaN layer above them. As for the electrical characteristics, there was no significant degradation in the mobility of the two-dimensional electron gas. The results indicate that selective thermal etching is a promising technique for device fabrication and is especially suitable for precise GaN layer removal when GaN-based devices are fabricated with an epitaxial layer transfer technique.

我们研究了在氢氨混合气氛中选择性热蚀刻对 Ga 极性和 N 极性 AlGaN/GaN 异质结构的晶体质量和电气特性的影响。结果表明，在我们的实验条件下，N 极性 GaN 的蚀刻速率低于 Ga 极性 GaN 的蚀刻速率，并且它们在几乎相同的活化能下表现出对工艺温度的相似依赖性。我们展示了使用薄的 AlGaN 层作为 Ga 和 N 极性的选择性蚀刻停止层。在蚀刻其上方的 GaN 层后，AlGaN 阻挡层表现出光滑的表面。至于电特性，二维电子气的迁移率没有明显下降。