Effects of KOH etching on the properties of Ga-polar n-GaN surfaces

Grigore Moldovan (1, 2) , Martin Roe (3) , Ian Harrison (3) , Menno Kappers (1) , Colin John Humphreys (1) , P D Brown (2)

1 DMSM - Department of Materials Science and Metallurgy [Cambridge University]
2 School of Mechanical, Materials, Manufacturing Engineering and Management
3 School of Mechanical, Materials and Manufacturing Engineering

The effects of a KOH treatment on the properties of n-type GaN surfaces and associated Au/n-GaN contacts were investigated by means of X-ray photoelectron spectroscopy, atomic force microscopy, reflection high energy electron diffraction, current-voltage and electron beam induced current characterisation. Ga-polar surfaces grown by molecular beam epitaxy and metal-organic chemical vapour deposition were compared. A decrease in electron barrier height and an increase in non-radiative recombination properties of Au/n-GaN contacts were found with KOH treatment, correlated with an increase of surface Ga vacancies, an increase of surface N-H2 content and a decrease of surface C contamination. A 0.3eV shift in the Ga3d peak position towards the valence band and a reduction in the dislocation contrast were observed for the case of molecular beam epitaxy grown GaN only, demonstrating that surface Ga vacancies and threading dislocations play only a limited role in defining the resultant metal/GaN contact properties. Accordingly, the surface atomic content and the resulting surface states following KOH treatment should be taken into consideration when appraising the electrical properties of n-GaN surfaces and the performance of associated metallic contacts.

Mots clés: Physical Sciences

Grigore Moldovan, Martin Roe, Ian Harrison, Menno Kappers, Colin John Humphreys, et al.. Effects of KOH etching on the properties of Ga-polar n-GaN surfaces. Philosophical Magazine, 2006, 86 (16), pp.2321-2332. ⟨10.1080/14786430500522628⟩. ⟨hal-00513652⟩