Pd/Zn/Pd/Au ohmic contacts to p-type In0.47Ga0.53As/InP

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Abstract
The electrical properties of Pd/Zn/Pd/Au ohmic contacts to p‐type In0.47Ga0.53As/InP have been investigated as a function of the ratio of the interfacial Pd and Zn layers and the annealing treatment. For as‐deposited contacts, the presence of an increasing thickness of interfacial Zn and Pd to ∼300 Å in the metallization resulted in a reduction in specific contact resistance, ρc, to a low value of 1.2×10−5 Ω cm2. Annealing of all of the contact configurations except the Zn=0 and 20 Å structures produced a reduction in ρc to a minimum value of 7.5×10−6 Ω cm2 at 500 °C. A critical thickness of the Zn≥50 Å and Pd≥100 Å interfacial layers was required in order to produce a significant reduction in ρc during annealing. These results have been interpreted in terms of the reaction between Pd and In0.47Ga0.53As and an associated doping at the near surface region by Zn atoms. Annealing of the contacts at temperatures of ≥450 °C resulted in significant intermixing of the metal layers and the In0.47Ga0.53As as revealed by Rutherford backscattering spectrometry and Auger depth profiling.