Schottky contact in P-HEMT wafer using metallization with Ge/Au/Ni/Au

An interface layer between a metal and a semiconductor, can either be an Ohmic or Schottky contact. Schottky is barrier height defined the rectifying properties of the device. In manufacturing semiconductor devices, Schottky contact on metal-semiconductor interface are essentially for achieving good rectifying properties. In this study, Schottky contact were fabricated on AlGaAs HEMTs structure. 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 and annealing temperatures (from 300^oC to 400^oC) were vary during fabrication process. Electrical characterizations after annealing are carried out using current-voltage (I-V) measurement are used to calculated Schottky barrier and Ideality Factor. The Schottky barrier increased with increasing annealing temperature until 400°C however Schottky barriers height and Ideality Factor does not varies much with metallization time. The highest Schottky barrier achieved is below 1.0eV with Ideality Factor 5.