OHMIC CONTACTS ON P-IN0.53GA0.47AS PREPARED BY ZN IMPLANTATION IRATE PD-BASED METALLIZATIONS

A new technique is presented for the fabrication of low-resistivity Oh mic contacts on p-In0.53Ga0.47As doped below 1X10(19) cm(-3) consistin g of dopant implantation into the contact metal and subsequent rapid t hermal annealing. Zn-implanted and annealed Pd/Au/Pt/Au, Pd/LaB6/Au, a nd Pd/Ge contacts exhibit drastically lowerer contact resistivity in c omparison to corresponding systems prepared without implantation. A re sistivity decrease by approximately one and a half orders of magnitude is observed in cases of Pd/Au/Pt/Au and Pd/LaB6/Au contacts. The lowe st value is found for Pd/Au/Pt/Au on p-In0.53Ga0.47As doped to 4x10(18 ) cm(-3) with 1X10(-6) Omega cm(2) whereas 1-2X10(-5) Omega cm(2) is o btained for Pd/Ge contacts on p-In0.53Ga0.47As doped to 7x10(18) cm(-3 ). The elemental redistribution and the interface morphology of anneal ed contacts have been studied with backside secondary ion mass spectro scopy and cross-sectional transmission electron microscopy. No contact penetration and a planar interface are found in the case of Pd/Ge, wh ereas significant penetration of contact components into the semicondu ctor and nonplanarity of the interface are observed in Pd/Au/Pt/Au and Pd/LaB6/Au contacts. In contacts annealed at conditions for minimal r esistivity the penetration depth is 200 and 105 nm, respectively. Impl anted Zn is redistributed toward the contact interface during thermal processing. Thus the resistivity lowering is attributed to enhanced p- doping by Zn, which diffused from the contact into the underlying semi conductor. Residual implantation damage is discussed as the essential cause of the comparably high resistivity of implanted and annealed Pd/ Ge contacts. (C) 1995 American Vacuum Society.