Copper-Gate AlGaN/GaN HEMTs with Low Gate Leakage Current

概要

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The application of copper to AlGaN/GaN HEMT gate will benefit from the superior electronic conductivity for narrow gate and low cost. In this paper, evaluation of AlGaN/GaN HEMT with copper gate was presented. For a device with gate length of 2μm and drain-source distance of 10μum, extrinsic transconductance is about 60mS/mm at the gate voltage of -3V and drain voltage of 8V. Maximum drain current density is found to be 400mA/mm under gate voltage of 5V and drain voltage of 15.9V. At gate voltage of -15V, gate leakage currents are found to be as low as 5.4×10^-8 (1.08μA/mm) under drain voltage of 0.1V. For comparison, two kinds of devices were fabricated with same process conditions except the gate metals, one is Cu (200nm) gate type by thermal evaporation and another is Ni/Au (50nm/50nm) gate type by electron beam evaporation. Comparable I-V performances were obtained for the two kinds of devices. Threshold voltage shift exists mainly due to the metal work function difference between Cu and Ni but gate leakage current is lower for Cu gate device than that for NiAu gate device. No adherence problem was found during these experiments. These results indicate that copper is another candidate as gate metallization for AlGaN/GaN HEMT.
社団法人電子情報通信学会の論文
2002-10-03