Dopant activation and ultralow resistance ohmic contacts to Si-ion-implanted GaN using pressurized rapid thermal annealing

Yu, Haijiang; McCarthy, L.; Xing, H.; Waltereit, H.; Shen, L.; Keller, S.; Denbaars, S. P.; Speck, J. S.; Mishra, U. K.
November 2004
Applied Physics Letters;11/29/2004, Vol. 85 Issue 22, p5254
Academic Journal
Activation annealing of Si implants in metalorganic-chemical-vapor-deposition-grown GaN has been studied for use in ohmic contacts. Si was implanted in semi-insulating GaN at 100 keV with doses from 5×1014 to 1.5×1016 cm-2. Rapid thermal annealing at ∼1500 °C with 100 bar N2 overpressure was used for dopant activation, resulting in a minimum sheet resistance of 13.9 Ω/square for a dose of 7×1015 cm-2. Secondary-ion-mass-spectroscopy measurements showed a post-activation broadening of the dopant concentration peak by 20 nm (at half the maximum), while x-ray triple-axis ω–2θ scans indicated nearly complete implant damage recovery. Transfer-length-method measurements of the resistance of Ti/Al/Ni/Au contacts to activated GaN:Si (5×1015 cm-2 at 100 keV) indicated contact resistances of 0.07 and 0.02 Ω mm for as-deposited and subsequently annealed contacts, respectively.


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