Semipolar (10-11) GaN growth on silicon-oninsulator substrates: Defect reduction and meltback etching suppression
Résumé
We demonstrate the growth of almost strain-free (10-11) semipolar GaN on silicon-on-insulator (SOI) substrates, with no meltback
etching 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 small
nucleation (111) facets, revealed through chemical etching of the topmost thin Si layer, we are able to diminish significantly the
overall dislocation density. Cathodoluminescence and scanning electron microscopy images at different stages of the growth
illustrate how the defect density reduction operates and confirm the complete suppression of meltback etching over the whole
2 in. wafer. Low temperature photoluminescence and optical reflectivity indicate that complete strain relaxation is closely
achieved (D0X at 3.473 ± 0.001 eV), compared to semipolar epilayers grown onto “bulk” silicon (D0X at 3.460 eV). Thanks to this
efficient strain relaxation, very thick layers, up to 9 μm, could be obtained crack-free.
Domaines
Sciences de l'ingénieur [physics]
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