Papers by Author: Jennifer K. Hite

Abstract: The growth of epitaxial graphene on C-face 6H-SiC substrates is investigated using pro-cess conditions that can form small, local areas of graphene. The thickness of SiC lost to Si sublimation is not completely countered by the thickness of the resulting graphene and so graphene-covered basins (GCBs) are formed. The GCBs are most likely nucleated at threading dislocations from the substrate. The GCB morphology exhibits ridges, similar to those found on continuous films. The GCBs expand through erosion of the surrounding SiC substrate walls, eventually coalescing into continuous films. The ratio of the Raman D and G peaks was used to estimate the crystallite length scale and it was found to be about 200 nm for small GCBs and > 1 m for continuous films.

Abstract: Homo- and heteroepitaxial 3C-SiC layers were grown on 4H-SiC step-free mesas. The yields of smooth, defect-free mesas were ~ 17% for both intentionally and unintentionally doped films, while those with screw dislocations and multiple stepped surfaces were ~ 22%. The electronic and structural properties of the mesas were found on a micrometer-sized length scale using µ-PL and µ-Raman, respectively. 3C-SiC mesas were found to have complete 3C-SiC coverage with some of the mesas having electronic defects, while other mesas were found to be defect-free.

Abstract: Field-effect transistors were fabricated on GaN and Al0.2Ga0.8N epitaxial layers grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrates. The threshold voltage VTH was higher when AlGaN was used as an active layer. VTH also increased with temperature due to the increased positive polarization charge at the GaN/AlN buffer/sapphire interfaces. Drain current increased at high temperatures even with more positive threshold voltage, which makes GaN-based FET devices attractive for high temperature operation.

Abstract: Epitaxial graphene (EG) grown on the carbon-face of SiC has been shown to exhibit high carrier mobilities, in comparison to other growth techniques amenable to wafer-scale graphene fabrication. The transfer of large area (>mm2) graphene films to substrates amenable for specific applications is desirable. We demonstrate the dry transfer of EG from the C-face of 4H-SiC onto SiO2, GaN and Al2O3 substrates via two approaches using either 1) thermal release tape or 2) a spin-on, chemically-etchable dielectric. We will report on the impact that these transfer processes has upon the electrical properties of the transferred EG films.