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Herein, the electrical and thermal performance of lateral AlGaN/GaN high electron mobility transistors (HEMTs) and metal‐insulator‐semiconductor field effect transistors (MISFETs) fabricated with 11 μm thick GaN buffer layers on 200 mm diameter Qromis Substrate Technology (QST) substrates are investigated. The QST substrate has a polycrystalline core engineered to be coefficient of thermal expansion (CTE)‐matched to GaN to minimize wafer bow and residual stress in the GaN film as a result of epitaxial growth. Raman spectroscopy is used to determine the biaxial residual stress in the GaN buffer of the as‐fabricated devices. Electrical characterization is demonstrated on the HEMTs including DC and pulsed output characteristics, DC transfer characteristics, Hall mobility, carrier concentration, sheet resistance, median transition frequency, and maximum stable gain. Finally, the thermal performance of the AlGaN/GaN MISFET is assessed via thermoreflectance thermal imaging at DC power densities up to 19 W mm−1. The thermal resistance of the MISFET, calculated using the peak temperature rises on the gate electrode for DC power densities <10 W mm−1, is measured to be 15.4 mm K W−1, which is comparable with state‐of‐the‐art GaN‐on‐Si lateral transistors. [ABSTRACT FROM AUTHOR]

Silicon (Si) is a common n-type donor in AlxGa1-xN; however, it induces bending of edge-type threading dislocations which can generate tensile stress in the film leading to the formation of channeling cracks in thick layers. Germanium (Ge) has previously been investigated as an alternative to Si for n-type doping of GaN, but its impact on film stress in AlxGa1-xN has not been investigated in detail. In this study, we employ in situ wafer curvature measurements combined with postgrowth characterization to investigate Ge doping of AlxGa1-xN (x = 0–0.62) layers grown on 6H-SiC by metalorganic chemical vapor deposition. It was found that Ge doping (n ∼ 1.6 × 1019 cm−3) of Al0.30Ga0.70N does not induce tensile stress during growth in contrast to that observed with a similar level of Si doping. In addition, the average inclination angle of edge dislocations was similar for undoped and Ge doped films indicating that Ge does not promote surface-mediated dislocation climb. High n-type doping was achieved in Ge doped AlxGa1-xN for lower Al fraction range (x < 0.5), but resistivity increased and carrier density decreased significantly for higher Al fractions. The results demonstrate Ge doping as a viable alternative to Si doping of AlxGa1-xN (x < 0.5) for achieving thick, crack-free layers. [ABSTRACT FROM AUTHOR]