GaN is widely used in applications that require either n-type or p-type doped semiconductors for charge carrier injection in different devices. A second advantage is the high mobility (>1200 cm 2 V −1 s −1) of the two-dimensional electron gas (formed at interfaces with e.g., AlN) that leads to low channel resistance and high current density (>1 A mm −1), and a breakdown field of 3.3 MV cm −1 that is 11 times higher than that of silicon (0.3 MV cm −1). Because of its geometric and electronic structure made up of covalent bonds between Ga and N, the wide energy band gap allows it to reach operating temperatures higher than 350 ☌. Among these compounds, GaN has shown impressive advantages. Many binary compounds also exhibit a very low electron effective mass, thus a high mobility, which makes them ideal candidates for developing high-speed devices. Due to the direct bandgap that most of these materials possess, efficient emission and absorption of light is allowed. The differences in values for both edge ( ρ d e ) and screw ( ρ d s ) dislocation densities, and correlation lengths ( L e, L s) found in the 690 nm GaN film, were associated with the better effective positron diffusion length ( L eff) of L eff GaN 2 = 43 ± 6 nm.īinary semiconductors, such as InN, AlN, GaAs, InAs, InP, GaN, AlSb, etc., and their alloys, cover an extended range of structures useful in high-end device technology. Positron depth profiling was evaluated through an experimental Doppler broadening spectroscopy (DBS) study, in order to quantify the effective positron diffusion length. Data resulting from high-resolution X-ray diffraction (HR-XRD) was mathematically modeled to extract dislocation densities and correlation lengths in the GaN film. The structure of the GaN film, AlN buffer layer, substrate, and their growth relationships were determined through high-resolution transmission electron microscopy (HR-TEM). The present article evaluates, in qualitative and quantitative manners, the characteristics (i.e., thickness of layers, crystal structures, growth orientation, elemental diffusion depths, edge, and screw dislocation densities), within two GaN/AlN/Si heterostructures, that alter their efficiencies as positron moderators.
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