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Reduced Contact Resistance and Improved Surface Morphology of Ohmic Contacts on GaN Employing KrF Laser Irradiation

Authors :
Grace Huiqi Wang
T. K. Chan
Hong-Yu Zheng
Yong-Lim Foo
Thomas Osipowicz
Sukant K. Tripathy
Ting-Chong Wong
Xincai Wang
Source :
Japanese Journal of Applied Physics. 50:04DF06
Publication Year :
2011
Publisher :
IOP Publishing, 2011.

Abstract

We employ excimer laser annealing for ohmic contact formation to n- and p-type GaN layers grown on sapphire substrates. The laser irradiation of the n-GaN layers led to increased nitrogen vacancies at the nitride surface, which promoted tunneling currents with a less resistive n-contact. For p-GaN layer, the laser irradiation increased the effective hole concentration that resulted in a reduced contact resistivity. The lowest specific contact resistance measured using the transmission line method was about 2.4 ×10-7 and 3.2 ×10-4 Ω cm2 for n- and p-contacts, respectively. Laser irradiation also resulted in a comparatively good surface morphology as compared to rapid thermal annealing, which in turn improved the transmittance of contacts for light extraction from active layers. It was found out that both the electrical and optical characteristics of the p-GaN contacts exhibited a good thermal stability and an improved transmittance in the blue–green spectral range. An increased forward current with a reduced ohmic contact resistance in such high thermal stable contacts enable the fabrication of GaN light emitting diodes.

Details

ISSN :
13474065 and 00214922
Volume :
50
Database :
OpenAIRE
Journal :
Japanese Journal of Applied Physics
Accession number :
edsair.doi.dedup.....e2302ab777b3c3b9de78f306709a1eab
Full Text :
https://doi.org/10.7567/jjap.50.04df06