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Formation of extremely low resistance Ti/Pt/Au ohmic contacts to p-GaAs

: Stareev, G.


Applied Physics Letters 62 (1993), Nr.22, S.2801-3
ISSN: 0003-6951
ISSN: 1077-3118
Fraunhofer HHI ()
annealing; contact resistance; gallium arsenide; gold; heavily doped semiconductors; iii-v semiconductors; ion beam effects; metallisation; ohmic contacts; platinum; titanium; tunnelling; p-type semiconductor-metal boundary; ar+ ion bombardment; heavily doped; effective cleaning; semiconductor surface; metal deposition; subsurface layer; extremely low resistivity; electrical properties; structural modifications; contact resistivity; optimal conditions; tunneling; mechanism; current flow; 420 to 530 degc; GaAs-au-pt-ti; GaAs

Nonalloyed Ti/Pt/Au contacts to heavily doped p-GaAs have been fabricated using effective cleaning of the semiconductor surface by bombardment with low energy Ar+ ions (60 eV) prior to the metal deposition. Short-time annealing cycles for 1 and 20 s were employed in order to restore the primary properties of the subsurface layer disordered during ion bombardment. Annealing at temperatures ranging from 420 to 530 degrees C provides formation of contacts with an extremely low resistivity of 2.8*10-8 Omega cm2. A definite correlation between electrical properties and structural modifications of the contact interface was found. Measurements of the contact resistivity at different ambient temperatures yielded a good quantitative agreement with the theoretically predicted values using the field-emission model. The results indicate that the metal-semiconductor junctions formed under optimal conditions are intimate and that tunneling is the dominant mechanism of the current flow.