Crystal and electrical properties of polycrystalline In1−xGaxAs thin films directly formed on insulators

Polycrystalline In_1−xGa_xAs thin films are promising for high-performance electronics on versatile substrates, including transistors, solar cells, optical communication devices, and infrared sensors. This study examines the effects of composition, deposition temperature, and impurity doping on the grain size, crystal orientation, nanostructure, and electrical properties of In_1−xGa_xAs layers, utilizing various evaluation methods with machine learning. The results demonstrate that the composition and deposition temperature significantly influence the crystallinity and crystal orientations. Higher In compositions and deposition temperatures yield In_1−xGa_xAs with enhanced crystallinity. The undoped samples exhibit n-type conduction, which is likely attributable to antisite defects. Increasing the In content and deposition temperature increases the electron concentration and mobility up to 3 × 10¹⁸ cm⁻³ and 310 cm² V⁻¹s⁻¹, respectively. Sn is an effective n-type dopant, facilitating the control of electron concentration within the range of 10¹⁷–10¹⁹ cm⁻³. These findings offer valuable insights into the application of In_1−xGa_xAs in high-performance electronic devices.