发表机构
University of Massachusetts Lowell（马萨诸塞大学洛厄尔分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过 HVPE 在多种取向衬底上实现 $\eta$-Ga$_2$O$_3$ 高温同质外延，优化工艺获得高速率厚膜生长，并揭示取向依赖的表面形貌演化。
AI 中文摘要
本文系统研究了在 (010)、(001) 和 ($\ar{2}$01) 原生衬底上通过卤化物气相外延（HVPE）进行 $\eta$-Ga$_2$O$_3$ 同质外延生长，覆盖了广泛的生长参数空间，并将生长温度最高提升至 1150 °C。生长动力学表现出对前驱体供应、温度、反应室压力以及镓源到衬底距离的强烈依赖。将 HCl 流量从 80 sccm 增加到 300 sccm，生长速率最高提升七倍；而将温度从 1050 °C 升高到 1150 °C，沉积速率几乎翻倍。在 1150 °C 下，常压生长的速率比 100 Torr 下高出 2.5 倍以上，而将 O$_2$ 流量降至 5 sccm 可进一步将生长速率提高到 14.3 μm/h，在 3 小时内制备出厚度达 42.9 μm 的薄膜。值得注意的是，在所有三种取向上均获得了相纯的同质外延层，晶体质量良好，(010)、(001) 和 ($\ar{2}$01) 外延层的摇摆曲线半高宽（FWHM）分别低至 63.4、66.6 和 42.8 角秒。表面形貌表现出显著的晶体学取向依赖性，并随 HVPE 生长条件强烈演化。特别是，($\ar{2}$01) 表面形成了清晰的台阶-平台形貌，局部 RMS 粗糙度低至 0.17 nm。这些结果将 $\eta$-Ga$_2$O$_3$ HVPE 同质外延扩展到更高温度区间，并展示了用于高速率生长厚且高质量外延层的宽工艺窗口，同时伴随强烈的取向依赖表面演化。
英文摘要
In this work, we systematically investigate homoepitaxial $β$-Ga$_2$O$_3$ growth by halide vapor phase epitaxy (HVPE) on (010), (001), and ($\bar{2}$01) native substrates over a broad growth parameter space, extending the growth temperature as high as 1150 $^\circ$C. The growth kinetics exhibit strong dependence on precursor supply, temperature, reactor pressure, and Ga-source-to-substrate distance. Increasing the HCl flow from 80 to 300 sccm enhances the growth rate by up to seven-fold, while increasing the temperature from 1050 to 1150 $^\circ$C nearly doubles the deposition rate. At 1150 $^\circ$C, atmospheric-pressure growth yields rates more than 2.5 times higher than those at 100 Torr, while reducing the O$_2$ flow to 5 sccm further increases the growth rate to 14.3 $μ$m/h, producing films up to 42.9 $μ$m thick in 3 h. Notably, phase-pure homoepitaxial layers with good crystalline quality are obtained across all three orientations, with low rocking-curve full width at half maximum (FWHM) values of 63.4, 66.6, and 42.8 arcsec for the (010), (001), and ($\bar{2}$01) epilayers, respectively. The surface morphology exhibits a pronounced crystallographic dependence and evolves strongly with the HVPE growth conditions. In particular, the ($\bar{2}$01) surface develops well-defined step-and-terrace morphology with local RMS roughness as low as 0.17 nm. These results extend $β$-Ga$_2$O$_3$ HVPE homoepitaxy into a higher-temperature regime and demonstrate a broad process window for high-rate growth of thick, high-quality epilayers with strongly orientation-dependent surface evolution.
