Ohmic contacts on p-GaN (Part I): investigation of different contact metals and their thermal treatment

摘要

The changes in contact resistivity and I-V curve linearity after annealing of Pd, Ni/Au, Cr/Au, Co/Au, Pt and Au contacts on p-GaN after tempering below and above 500 ℃ have been investigated. CTLM-layered structures on p-GaN were thermally stressed and electrically analyzed. The I-V curve linearity as a measure of ohmic behavior has been derived from the correlation coefficient of the I-V curves. Below 500 ℃ the Pd, Ni/Au, Cr/Au and Co/Au contacts become ohmic after annealing. The best final values of the specific contact resistance ρ_c after annealing increase in the sequence Ni/Au, Pd, Co/Au, Cr/Au, Au and Pt. After annealing above 500 ℃ the contact resistance increases for all contact materials and the linearity decreases. A competition between the formation of reaction phases at the interface and the decomposition of the p-GaN epi-layer in a probable reason for this behavior.