Abstract
Ultra low resistance ohmic contacts are fabricated on n-GaSb grown by molecular beam epitaxy. Different doping concentrations and n-GaSb thicknesses are studied to understand the tunneling transport mechanism between the metal contacts and the semiconductor. Different contact metallization and anneal process windows are investigated to achieve optimal penetration depth of Au in GaSb for low resistances. The fabrication, electrical characterization, and microstructure analysis of the metal-semiconductor interfaces created during ohmic contact formation are discussed. The characterization techniques include cross-sectional transmission electron microscopy and energy dispersive spectroscopy. Specific transfer resistances down to 0.1 Ω mm and specific contact resistances of 1 × 10−6 Ω cm2 are observed.
Highlights
To date, ohmic contacts to n-GaSb are mainly Au-based[7,8,9,10,11,12,13,14] and Pd-based.[15,16,17,18] The first attempts at making ohmic contacts to n-GaSb were modeled on the same contact scheme used for n-GaAs.[19]
This typically consists of a Ni/Ge/Au metallization sequence which has achieved a minimum contact resistance of about 0.4 cm2.12 the result is poor due to an unoptimized temperature window for annealing, a lack of a diffusion barrier in the metal sequence, partial oxide removal, and poor vacuum conditions for metal evaporation
There is a report of Te/Au (60/340 nm) metallization that yields a specific contact resistance of 1 × 10−6 cm[2] when annealed at 380 ◦C for 1 h and 450 ◦C for 2 s
Summary
Ohmic contacts to n-GaSb are mainly Au-based[7,8,9,10,11,12,13,14] and Pd-based.[15,16,17,18] The first attempts at making ohmic contacts to n-GaSb were modeled on the same contact scheme used for n-GaAs.[19]. Electrical and microstructure analysis of nickel-based low-resistance ohmic contacts to n-GaSb
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