Abstract
Selective area growth of cubic gallium nitride is investigated in a plasma assisted molecular beam epitaxy setup. 380 μm thick silicon (001) and 10 μm thick 3C-silicon carbide (001), grown on 500 μm silicon (001), were used as substrates and structured with silicon dioxide masks. Selective area growth on silicon and 3C-silicon carbide was tested for both thermal and plasma deposited oxides. Multiple growth series showed that gallium nitride coverage of silicon dioxide vanished at growth temperatures of 870 °C for silicon substrates and at a surface temperature of 930 °C for 3C-silicon carbide substrates. Whereas gallium nitride is grown in its hexagonal form on silicon substrates, phase pure cubic gallium nitride could selectively be grown on the 3C-silicon carbide template. The cubic phase is verified by high resolution x-ray diffraction and low temperature photoluminescence measurements. The photoluminescence measurements prove that gallium nitride condensed selectively on the 3C-silicon carbide surfaces uncovered by silicon dioxide.
Highlights
Group III nitrides, often examined in the hexagonal phase, can be grown in the metastable cubic zinc blende phase
State of the art epitaxial cubic GaN (c-GaN) thin films grown on 3C-SiC(001) with a thickness of less than 1 μm show full width at half maximum (FWHM) of symmetric (002) x-ray diffraction (XRD) rocking curves in the order of 30 arc min
scanning electron microscopy (SEM) images of the surfaces show that the plasma deposited SiO2 (PD-SiO2) is very grainy
Summary
Group III nitrides, often examined in the hexagonal phase, can be grown in the metastable cubic zinc blende phase. Patterned substrates could be utilized to improve crystal quality by reducing dislocation density and smooth the surface of epilayers. Liu and Bayram et al 3,4 revealed that if two hexagonal GaN growth fronts merge with a tetrahedron bonding angle of 109.47○, cubic GaN via a wurtzite to cubic phase transition is formed on (111) faceted Si (001) substrates. Utilizing this hetero-phase epitaxy implies selective growth of GaN on the structures’ (111) facets. On Si (111) facets, GaN is grown in its stable hexagonal phase; hexagonal interlayers are always produced between the substrate and the zinc blende GaN, reducing phase purity of the coalesced epilayer. dislocation free cubic GaN growth without initial hexagonal nucleation was observed in V-grooves in 3C-SiC.
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