This study explores the epitaxial relationship and electrical properties of α-Ga₂O₃ thin films deposited on a-plane, m-plane, and r-plane sapphire substrates. We characterize the thin films by X-ray diffraction and Raman spectroscopy, and elucidate thin film epitaxial relationships with the underlying sapphire substrates. The oxygen vacancy concentration of α-Ga₂O₃ thin films on m-plane and r-plane sapphire substrates are higher than α-Ga₂O₃ thin film on a-plane sapphire substrates. All three thin films have a high transmission of over 80% in the visible and near-ultraviolet regions, and their optical bandgaps stay around 5.02–5.16 eV. Hall measurements show that the α-Ga₂O₃ thin film grown on r-plane sapphire has the highest conductivity of 2.71 S/cm, which is at least 90 times higher than the film on a-plane sapphire. A similar orientation-dependence is seen in their activation energy as revealed by temperature-dependent conductivity measurements, with 0.266, 0.079, and 0.075 eV for the film on a-, m-, r-plane, respectively. The origin of the distinct transport behavior of films on differently oriented substrates is suggested to relate with the distinct evolution of oxygen vacancies at differently oriented substrates. This study provides insights for the substrate selection when growing α-Ga₂O₃ films with tunable transport properties.

A suitable contacting scheme for p-(Al)GaN facilitating quick feedback and accurate measurements is proposed in this study. 22 nm p⁺-GaN followed by 2 nm p-In_0.2Ga_0.8N was grown on p-type layers by metal-organic chemical vapor deposition. Samples were then cut into squares after annealing and contact electrodes using In balls were put at the corners of the squares. Good linearity between all the electrodes was confirmed inI–V curves during Hall measurements even with In metal. Serval samples taken from the same wafer showed small standard deviation of ~ 4% for resistivity, Hall mobility and hole concentration. The influence of contact layer on the electrical characteristics of bulk p-type layers was then investigated by step etching technique using inductively coupled plasma etching and subsequent Hall-effect measurements. Identical values could be obtained consistently when a 28 nm non-conductive layer thickness at the surface was taken into account. Therefore, the procedures for evaluating the electrical properties of GaN-based p-type layers just using In balls proposed in this study are shown to be quick and useful as for the other conventional III–V materials.

Sb-doped β-Ga2O3 crystals were grown using the optical floating zone (OFZ) method. X-ray diffraction data and X-ray rocking curves were obtained, and the results revealed that the Sb-doped single crystals were of high quality. Raman spectra revealed that Sb substituted Ga mainly in the octahedral lattice. The carrier concentration of the Sb-doped single crystals increased from 9.55×1016 to 8.10×1018cm-3, the electronic mobility depicted a decreasing trend from 153.1 to 108.7cm2·V-1·s-1, and the electrical resistivity varied from 0.603 to 0.017 Ω·cm with the increasing Sb doping concentration. The un-doped and Sb-doped β-Ga2O3 crystals exhibited good light transmittance in the visible region; however, the evident decrease in the infrared region was caused by increase in the carrier concentration. The Sb-doped β-Ga2O3 single crystals had high transmittance in the UV region as well, and the cutoff edge appeared at 258 nm.

以卤钨灯积分球光源作为辐射源、用宽谱段陷阱探测器同步监测的传统稳定性参数测试方法存在光谱带宽不匹配、数据对齐困难等问题，导致测量准确性不能保证。因此提出用多角度偏振成像仪自身的图像数据替代陷阱探测器监测数据的方案，对多角度偏振成像仪12个通道数据分别进行小波分解，提取出各波段的光源能量变化用于稳定性测量数据校正，有效去除光源稳定性影响，提升仪器稳定度参数测量准确性。用该方案扣除光源波动后，载荷的非稳定性参数结果从0.153%减小至0.031%。提取出的同一波段三检偏方向光源辐射能量变化趋势高度一致，对多帧图像法信噪比计算结果提升更明显，有力证明方案的有效性。该方案可用于各类成像型遥感仪器的稳定性参数测试。