Performance comparison of Cu and Ni gates for deep submicrometer AlGaN/GaN HFETs

摘要

Copper (Cu) was investigated as the gate contact metallization in AlGaN/GaN heterostructure field-effect transistors (HFETs). For comparison, Nickel/Gold (Ni/Au) gate devices were fabricated on the same sample using electron beam lithography. Both metallization schemes yielded comparable transconductance characteristics: the maximum extrinsic transconductance reached 290 mS/mm. At gate voltage of -20 V, the reverse current for the Cu Schottky contact was roughly one to two orders of magnitude lower than that of Ni/Au contact. For Cu/Au gate devices, the product of current gain cut-off frequency (f_T) and gate length L_G improved by 15% compared to Ni/Au gate devices. The power gain cut-off frequency (f_(max)) also improved by at least 15%.