Focused gas beam injection for efficient ammonia-molecular beam epitaxial growth of III-nitride semiconductors

A focused gas beam injection is proposed for high-efficiency ammonia molecular beam epitaxial growth of III-nitride. This new injector design is based on a double, coaxial radial high-conductance geometry, which allows rotation-free growth with fast gas switching. The injection profile is characterized through a mobile ion gauge and is then compared to simulations, where experimental results show that up to 27% of the injected molecules reach the surface of the substrate. The injector is tested for the growth of GaN layers, and high-resolution x-ray diffraction rocking curves of a 1 μm-thick GaN layer grown on a commercial GaN template (1 μm-thick layer of GaN on Si) was measured around the 002 Bragg condition and a full width at half maximum of 594 arc sec was obtained. Low-temperature photoluminescence for the same layer shows intense band edge emission and a low yellow luminescence. Hall measurements of the silicon-doped layers show high carrier concentrations up to 2 × 1019 cm−3 and a corresponding mo...