Two techniques to reduce the contact resistance RC in AlGaN/GaN HFETs have been investigated. Both techniques involve the formation of a matrix of 100 nm diameter pinholes in resist in the contact region using e-beam direct-write lithography. In the first technique, silicon is implanted through the matrix to form doped/damaged filaments extending through the AlGaN cap to the 2DEG. In the second technique, sputtering is used to remove the AlGaN from the pinhole, allowing metal to directly contact the 2DEG. RC was measured as a function of anneal temperature. Si implanted samples gave RC = 0.34 Ω mm for 800°C annealing, roughly half the value of control samples. Sputter etch samples had RC comparable to that of controls.

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Conference 2nd International Workshop on Nitride Semiconductors, IWN 2002
Amaya, R, Bardwell, J., Webb, J., Tang, H., MacElwee, T.W., & Tarr, N.G. (2002). Contact resistance reduction in AlGaN/GaN heterostructure field effect transistors. Presented at the 2nd International Workshop on Nitride Semiconductors, IWN 2002. doi:10.1002/pssc.200390032