Semipolar (10-11) GaN growth on silicon-oninsulator substrates: Defect reduction and meltback etching suppression

Description

We demonstrate the growth of almost strain-free (10-11) semipolar GaN on silicon-on-insulator (SOI) substrates, with no meltbacketching and with a defect density strongly reduced compared to semipolar templates grown on patterned silicon substrates.This is carried out using SOI substrates with a very thin (∼150 nm) 6° off (001) Si top layer. By resorting to very smallnucleation (111) facets, revealed through chemical etching of the topmost thin Si layer, we are able to diminish significantly theoverall dislocation density. Cathodoluminescence and scanning electron microscopy images at different stages of the growthillustrate how the defect density reduction operates and confirm the complete suppression of meltback etching over the whole2 in. wafer. Low temperature photoluminescence and optical reflectivity indicate that complete strain relaxation is closelyachieved (D0X at 3.473 ± 0.001 eV), compared to semipolar epilayers grown onto "bulk" silicon (D0X at 3.460 eV). Thanks to thisefficient strain relaxation, very thick layers, up to 9 μm, could be obtained crack-free.

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