AI 中文总结
研究通过低压化学气相沉积在不同切角蓝宝石衬底上生长锗掺杂β-Ga₂O₃薄膜，发现增加切角可提升薄膜质量和迁移率，6°切角样品室温迁移率达117 cm²/V s，通过多种模型分析了载流子浓度等数据。
AI 中文摘要
在本工作中，使用低压化学气相沉积（LPCVD）在具有0°、2°、6°和8°切角的c面蓝宝石衬底上异质外延生长高质量锗掺杂（-201）β-Ga₂O₃薄膜。增加蓝宝石切角促进了台阶流生长，改善了台面排列，降低了表面粗糙度并提高了晶体质量。通过X射线衍射和拉曼光谱确认了具有强（-201）择优取向的纯相单斜β-Ga₂O₃，X射线光电子能谱显示O/Ga比为1.48的近化学计量组成。电输运性质强烈依赖于衬底切角，室温霍尔迁移率随着切角从0°增加到6°，在载流子浓度范围为1.43×10¹⁷至2.75×10¹⁸ cm⁻³时从15增加到117 cm²/V s。6°切角样品在载流子浓度为1.43×10¹⁷ cm⁻³时实现了117 cm²/V s的室温迁移率，在128 K和载流子浓度为8.96×10¹⁶ cm⁻³时实现了337 cm²/V s的峰值低温迁移率，代表了在蓝宝石衬底上生长的锗掺杂β-Ga₂O₃薄膜报道的最高室温及低温迁移率。使用电荷中性和玻尔兹曼输运模型结合施主激活以及极性光学声子、电离杂质、中性杂质、声学形变势和位错散射机制对载流子浓度和迁移率数据进行了分析。拟合揭示了12.5 - 19 meV的浅施主激活能、80 meV的更深施主能级、低受主补偿（<5×10¹⁵ cm⁻³）以及约10⁹ cm⁻²的位错密度。
英文摘要
In this work, high-quality Ge-doped (-201) $β$-Ga$_2$O$_3$ thin films were heteroepitaxially grown on c-plane sapphire substrates with offcut angles of 0 deg, 2 deg, 6 deg, and 8 deg using low-pressure chemical vapor deposition (LPCVD). Increasing sapphire offcut promoted step-flow growth, resulting in improved terrace alignment, reduced surface roughness, and enhanced crystalline quality. Phase-pure monoclinic $β$-Ga$_2$O$_3$ with strong (-201) preferential orientation was confirmed by X-ray diffraction and Raman spectroscopy, while X-ray photoelectron spectroscopy revealed near-stoichiometric composition with an O/Ga ratio of 1.48. Electrical transport properties exhibited a strong dependence on substrate offcut angle, with room-temperature Hall mobility increasing from 15 to 117 cm$^2$/V s as the offcut angle increased from 0 deg to 6 deg, across carrier concentrations spanning $1.43 \times 10^{17}$ to $2.75 \times 10^{18}$ cm$^{-3}$. The 6 deg offcut sample achieved a room-temperature mobility of 117 cm$^2$/V s at a carrier concentration of $1.43 \times 10^{17}$ cm$^{-3}$ and a peak low-temperature mobility of 337 cm$^2$/V s at 128 K with a carrier concentration of $8.96 \times 10^{16}$ cm$^{-3}$, representing the highest reported room-temperature and low-temperature mobilities for Ge-doped $β$-Ga$_2$O$_3$ films grown on sapphire substrates. Carrier concentration and mobility data were analyzed using charge-neutrality and Boltzmann transport models incorporating donor activation together with polar optical phonon, ionized impurity, neutral impurity, acoustic deformation potential, and dislocation scattering mechanisms. The fitting revealed shallow donor activation energies of 12.5-19 meV, a deeper donor level at 80 meV, low acceptor compensation ($< 5 \times 10^{15}$ cm$^{-3}$), and threading dislocation densities on the order of $10^9$ cm$^{-2}$.
