Au/Pt/Ti contacts to p-In0.53Ga0.47As and n-InP layers formed by a single metallization common step and rapid thermal processing

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Abstract
We have demonstrated the viability of depositing a thick Au bonding pad on top of Pt/Ti contacts on both p‐InGaAs and n‐InP within a single evaporation prior to heat treatment. This eliminates the usual post‐sinter Au plating process. In particular, Au (500 nm)/Pt (60 nm)/Ti (50 nm) common contacts to Zn‐doped 5×1018 cm−3 p‐In0.53Ga0.47As and S‐doped 1×1018 cm−3 n‐InP were formed within a single pumpdown electron‐gun evaporation and subsequently a single sintering process by means of rapid thermal processing. The lowest resistivity of these ohmic contacts were found to be 0.11 and 0.13 Ω mm (5.5×10−7 and 8×10−6 Ω cm2) for the p and n contacts, respectively. These values were achieved as a result of heating at 450 °C for 30 sec. This heat treatment caused a limited reaction at the Au‐Pt and Pt‐Ti interfaces, which did not lead to any significant intermixing of the Ti and Au. Thus, no significant indiffusion of the Au thorough the Pt barrier was observed and contact degradation did not occur. The stress of the as‐deposited trilayer structure on InP was found to be 3×108 dyne cm2 tensile and increased to about 2×109 dyn cm2 as a result of the rapid thermal processing at 450 °C