Chemical beam epitaxy of gallium nitride on silicon: Use of silicon carbide as template and selective area growth

In this dissertation a pure chemical beam epitaxy (CBE) process is utilized to grow GaN on Si. The formation of an amorphous nitride layer on Si immediately upon initiation of the N gas precursor (NH₃) is alleviated by forming a thin SiC template layer prior to deposition. This layer is simply prepared by converting Si into SiC upon exposure to a Ga precursor, namely triethyl gallium (TEG). In situ time of flight mass spectroscopy of recoil ions (TOF MSRI) and ex situ XPS, SEM, and XRD characterization techniques were employed to optimize the parameters of the substrate carbonization and subsequent GaN deposition processes.; Crystalline 3C-SiC layers well oriented with the substrate are produced on Si(100) and Si(111) but they have a rough surface. The optimized exposure conditions are 800°C for substrate temperature and 2 min exposure duration. Single crystal GaN thin films on carbonized Si(111) are deposited, with growth rates as high as 300 nm/hr. Mixed cubic and hexagonal GaN thin films on carbonized Si(100) are obtained. The growth proceeds in a three-dimensional mode, which results in GaN thin films with a rough surface. The surface morphology of GaN/Si deteriorates with greater carbonization, namely with higher temperature and longer time TEG exposure.; We have also explored selective area growth (SAG) of GaN with CBE. Conventional silicon nitride and oxide are used as mask materials as well as BN for its superior chemical and thermal resistance. A photo-assisted reactive ion etching using BCl₃/Cl₂/N₂ plasma chemistries was developed and utilized for patterning GaN and BN. This process yields good etch rates and reduced surface damage. In situ TOF MSRI analysis shows the absence of GaN nucleation on SiN_x, SiO₂ and BN surfaces over a wide range of substrate temperatures. Upon regrowth of GaN on BN and SiO₂ patterned RF MBE grown GaN, micro-size overgrown features with vertical walls are obtained. The SAG GaN thin films were characterized for field emission properties.; Finally in appendices A and B, I also showed (i) a pure CBE process for GaN deposition on sapphire and (ii) an extensive study of TiAlN oxidation using TOF-MSRI and XPS.