Lateral diffusion effects in AuGe based source-drain contacts to AllnAs/InGaAs/InP doped channel MODFETs |
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Authors: | A A Iliadis J K Zahurak T Neal W T Masselink |
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Affiliation: | (1) Electrical Engineering Department, University of Maryland, 20742 College Park, Maryland;(2) Micron Technologies Inc., 83706 Boise, ID;(3) Microelectronics Research Laboratory, 21045 Columbia, MD;(4) Institute for Physics, Humboldt University Berlin, Invalidenstrasse 110, D-10439 Berlin, Germany |
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Abstract: | We have investigated the formation of source-drain AuGe/Au and Ni/AuGe/Ni/Au alloyed ohmic contacts to AlInAs/InGaAs/InP doped
channel MODFETs, and observed lateral diffusion of the contact system after the standard annealing procedure at the temperature
range of 185 to 400°C. Auger depth profiling of contacts annealed at 250°C, revealed that Au(Ge) diffused through the top
InGaAs and AlInAs layers into the active InGaAs layer, but had reduced penetration into the AlInAs buffer layer. This reduction
in diffusion along the depth axis at the AlInAs buffer layer boundary is believed to result in enhanced lateral diffusion
and the observed lateral encroachment of the contacts. Both Au and Ni containing contact systems showed similar behavior in
terms of lateral diffusion with encroachment extending between 0.25 and 0.5 μm at the periphery of the contacts for annealing
temperatures between 300 and 400°C. A controlled ramp-to-peak temperature annealing procedure is developed to suppress such
lateral diffusion effects. Low temperature annealing (250°C) using this procedure resulted in equally low contact resistance
values (∼0.1Θ-mm) and no lateral diffusion. It is concluded that in thin multilayered structures the modified annealing procedure
presented here, is necessary for optimal ohmic contact formation. |
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Keywords: | AlInAs/InGaAs/InP ohmic contacts AuGe based contacts MODFETs |
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