Pd/Ge/Ti/Au ohmic contact to AlGaAs/InGaAs pseudomorphic high electron mobility transistor with an undoped cap layer
Open Access
- 3 November 1997
- journal article
- research article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 71 (18) , 2656-2658
- https://doi.org/10.1063/1.120169
Abstract
The Pd/Ge/Ti/Au ohmic contact to AlGaAs/InGaAs pseudomorphic high electron mobility transistor was investigated with the etch depth of an undoped GaAs/AlGaAs cap layer. The contact resistivity decreases from 9.5×10 −5 to 2.3×10 −6 Ω cm 2 when the contacts were formed on a n- Al 0.23 Ga 0.77 As layer by removing the undoped cap layer. X-ray diffraction results show that the good ohmic contact is due to the formation of Au 2 Al as well as β-AuGa. Both compounds play a role to create group-III vacancies, followed by the incorporation of Ge into group-III vacancies, namely, creation of free electron below the contact. This results in the considerable elimination of contact resistivity by lowering the effective tunneling barrier.Keywords
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