Improved morphology for ohmic contacts to AlGaN/GaN high electron mobility transistors using WSix- or W-based metallization

• Published in: Applied physics letters 2003-06, Vol.82 (22), p.3910-3912
• Main Authors: Luo, B., Ren, F., Fitch, R. C., Gillespie, J. K., Jenkins, T., Sewell, J., Via, D., Crespo, A., Baca, A. G., Briggs, R. D., Gotthold, D., Birkhahn, R., Peres, B., Pearton, S. J.
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.1579845

A comparison was made of specific contact resistivity and morphology of Ti/Al/Pt/WSi/Ti/Au and Ti/Al/Pt/W/Ti/Au ohmic contacts to AlGaN/GaN heterostructures relative to the standard Ti/Al/Pt/Au metallization. The W- and WSi-based contacts show comparable specific resistivities to that of the standard contact on similar layer structures, reaching minimum values of ∼10−5 Ω cm2 after annealing in the range 850–900 °C. However, the W- and WSi-based contacts exhibit much smoother surface morphologies, even after 950 °C annealing. For example, the root-mean-square roughness of the Ti/Al/Pt/WSi/Ti/Au contact annealed at 950 °C was unchanged from the as-deposited values whereas the Ti/Al/Pt/Au contact shows significant deterioration of the morphology under these conditions. The improved thermal stability of the W- and WSix-based contacts is important for maintaining edge acuity during high-temperature operation.