Surface Morphology and Microstructure Evolution of Single Crystal Diamond during Different Homoepitaxial Growth Stages

Homoepitaxial growth of step-flow single crystal diamond was performed by microwave plasma chemical vapor deposition system on high-pressure high-temperature diamond substrate. A coarse surface morphology with isolated particles was firstly deposited on diamond substrate as an interlayer under hillock growth model. Then, the growth model was changed to step-flow growth model for growing step-flow single crystal diamond layer on this hillock interlayer. Furthermore, the surface morphology evolution, cross-section and surface microstructure, and crystal quality of grown diamond were evaluated by scanning electron microscopy, high-resolution transmission electron microcopy, and Raman and photoluminescence spectroscopy. It was found that the surface morphology varied with deposition time under step-flow growth parameters. The cross-section topography exhibited obvious inhomogeneity in crystal structure. Additionally, the diamond growth mechanism from the microscopic point of view was revealed to illustrate the morphological and structural evolution.

Stable Electron Concentration Si-doped β-Ga2O3 Films Homoepitaxial Growth by MOCVD

To obtain high-quality n-type doped β-Ga2O3 films, silane was used as an n-type dopant to grow Si-doped β-Ga2O3 films on (100) β-Ga2O3 substrates by metal-organic chemical vapor deposition (MOCVD). The electron concentrations of the Si-doped β-Ga2O3 films obtained through experiments can be stably controlled in the range of 6.5 × 1016 cm−3 to 2.6 × 1019 cm−3, and the ionization energy of Si donors is about 30 meV, as determined by analysis and calculation. The full width at half maxima of the rocking curves of the (400) crystal plane of all doped films was less than 500 arcsec, thus showing high crystal quality, while the increase of the doping concentration increased the defect density in the β-Ga2O3 films, which had an adverse effect on the crystal quality and surface morphology of the films. Compared with heteroepitaxial Si-doped β-Ga2O3 films, homoepitaxial Si-doped β-Ga2O3 films exhibited higher quality, lower defect density, and more stable electron concentration, which make them more conductive for preparing Ga2O3-based power devices.