The influence of interstitial Ga and interfacial Au2P3 on the electrical and metallurgical behavior of Au-contacted III-V semiconductors

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Abstract
The introduction of a very small amount of Ga into Au contact metallization on InP is shown to have a significant effect on both the metallurgical and electrical behavior of that contact system. Ga atoms in the interstices of the Au lattice are shown to be effective in preventing the solid‐state reactions that normally take place between Au and InP during contact sintering. In addition to suppressing the metallurgical interaction, the presence of small amounts of Ga is shown to cause an order of magnitude reduction in the specific contact resistivity. Evidence is presented that the reactions of GaP and GaAs with Au contacts are also drastically affected by the presence of Ga. The sintering behavior of the Au‐GaP and the Au‐GaAs systems (as contrasted with that of the Au‐InP system) is explained as due to the presence of interstitial Ga in the contact metallization. Finally the large, two‐to‐three order of magnitude drop in the contact resistance that occurs in the Au‐InP system upon sintering at 400 °C is shown to be a result of the formation of an Au2P3 layer at the metal‐semiconductor interface. Contact resistivities in the 10−6 Ω cm2 range are obtained for as‐deposited Au on InP when a thin (20 Å) layer of Au2P3 is introduced between the InP and the Au contacts.