Premium
Unintentional doping in GaN assessed by scanning capacitance microscopy
Author(s) -
Sumner J.,
Bakshi S. Das,
Oliver R. A.,
Kappers M. J.,
Humphreys C. J.
Publication year - 2008
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200778567
Subject(s) - conductivity , materials science , doping , scanning electron microscope , epitaxy , analytical chemistry (journal) , sapphire , coalescence (physics) , impurity , scanning capacitance microscopy , capacitance , optoelectronics , layer (electronics) , nanotechnology , chemistry , optics , electrode , composite material , scanning confocal electron microscopy , laser , physics , organic chemistry , chromatography , astrobiology
Using scanning capacitance microscopy (SCM) we observe a layer of unintentional n‐type conductivity in GaN/sapphire epilayers in a region adjacent to the GaN/sapphire interface. It is shown to have a carrier concentration of (1.66 ± 0.08) × 10 18 cm –3 . Secondary ion mass spectroscopy (SIMS) data from a similar sample suggests that the n‐type conductivity in this region results from unintentional oxygen incorporation. Various doped regions are also observed in epitaxial lateral over‐growth (ELOG) samples. GaN initially grows through a SiN x mask forming faceted stripes, which exhibit unintended n‐type conductivity. Magnesium is used to enhance stripe coalescence, resulting in p‐type regions. The top layer, grown following coalescence, appears non‐conducting. The different electron concentrations found within the ELOG cross‐section could correspond to the different facets formed during growth which may indicate that the changes in carrier concentration reflect the rate of impurity incorporation on each facet. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)