Integration of GaN and Diamond Using Epitaxial Lateral Overgrowth

Growth of single-crystalline GaN on polycrystalline diamond is reported for the first time. The structure was achieved using a combined process including selective diamond growth on GaN/Si wafers using hot filament chemical vapor deposition (CVD) and epitaxial lateral overgrowth of GaN on the window region between then above the diamond stripes via metal organic CVD. Optimization of the growth was performed by varying the ammonia to trimethylgallium mole ratio (V/III), chamber pressure, and temperature in the range of 8000-1330, 40-200 Torr, and 975-1030 °C, respectively. A lower pressure, higher V/III ratio, higher temperature, and GaN window mask openings along [11̅00] resulted in enhanced lateral growth of GaN. Complete lateral coverage and coalescence of GaN were achieved over a [11̅00]-oriented 5 μm-wide GaN window between 5 μm diamond stripes when using V/III = 7880, P = 100 Torr, and T = 1030 °C. The crystalline quality of overgrown GaN was confirmed using cross-sectional scanning electron microscopy, high-resolution X-ray diffraction, micro-Raman spectroscopy, transmission electron microscopy, and selective-area electron diffraction.