AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM2-ThA

Paper EM2-ThA10
In-situ Formation, Reactions, and Electrical Characterization of MBE Grown Metal/Semiconductor Interfaces

Thursday, November 5, 1998, 5:00 pm, Room 316

Session: Non-destructive Testing and In-situ Diagnostics
Presenter: L.C. Chen, University of Minnesota
Authors: L.C. Chen, University of Minnesota
D.A. Caldwell, University of Minnesota
T.G. Finstad, University of Oslo, Norway
C.J. Palmstrom, University of Minnesota
Correspondent: Click to Email
An in-situ probe station is used for the determination of the electronic properties of interfaces being modified in an MBE system. After MBE growth of the semiconductor structures, contacts were formed by metal deposition through a removable molybdenum shadow mask. An abrupt change in doping profile serves as a marker layer to allow doping density versus depth profile measurements obtained from capacitance-voltage (C-V) to be used to measure the position of the electrical metal/semiconductor interface relative to the marker layer, allowing metal/semiconductor reaction kinetics to be determined electrically in-situ. C-V measurements on n/n@super +@ GaAs structures were used to monitor the Ni/GaAs reaction and subsequent GaAs regrowth. The measurements indicated that 500Å of Ni consumes 700Å of GaAs during Ni@sub 3@GaAs formation, which is in excellent agreement with RBS and cross-sectional TEM measurements. Exposure of Ni@sub 3@GaAs to As@sub 4@ at 300°C results in the formation of NiAs at the surface and epitaxially regrown GaAs at the Ni@sub 3@GaAs/GaAs interface. The doping profiles indicated the complete regrowth of the 700Å GaAs beneath the contact. In-situ current-voltage (I-V) measurements of the NiAs/regrown-GaAs interfaces showed good Schottky behavior (V@sub bn@=0.87 V, n=1.08). C-V measurements showed further that the net electrically active donor density 2000Å beneath the contact changed during the different stages of reaction; it was 9.0x10@super 16@ (after Ni deposition), 6.5x10@super 16@ (after complete Ni@sub 3@GaAs formation), 5.Ox1O@super 16@ (after subsequent GaAs regrowth), and 9.0xl0@super 16@ (after an additional 585°C anneal). This results from the formation of point defects in the underlying GaAs during the reactions, which are eliminated by a 585°C anneal. In-situ electrical measurements on MBE-grown epitaxial metallic compound/Ga@sub 1-x@Al@sub x@As heterostructures grown on various surface terminations before and after annealing with emphasis on Sc@sub x@Er@sub 1-x@As structures will also be presented.