Ohmic Contact in P-HEMT Wafer Using Metallization with Ge/Au/Ni/Au
In this study, Ohmic contact were fabricated on AlGaAs HEMTs structure. A good metal-semiconductor interface are essentially for achieving lower specific contact resistance. An AlGaAs epi wafer was supply by the vendor. AlGaAs substrate was cleaned using wet chemical etching. Electrodes were fabricated through a sequenced of lithography, cleaning, sputtering and lift-off processes. The electrodes were made with metal layers of Ge, Au and Ni. Parameters such as metal thickness, annealing temperatures (from 300°C to 400°C) and annealing time were varies during fabrication process. Electrical characterizations after annealing are carried out using transmission line method (TLM) to obtain the specific contact resistance. Annealing temperature between 340°C to 360°C produced contact resistance below 5 x 10ˉ³Ω/cm-2.