Ohmic contact to AlGaN/GaN HEMT with electrodes in contact with heterostructure interface

Abstract

In order to alleviate the negative impacts of high temperature (850 °C) annealing on high electron mobility transistor (HEMT) technology, a process required only low temperature annealing (less than 600 °C) was introduced to form ohmic contact to HEMT. By the process, the electrode was in contact with the AlGaN/GaN interface. The value of specific contact resistivity (ρc) of the ohmic contact was 6.29 × 10−5 Ω cm2. An improved HEMT power device was presented. For comparison, a conventional device with Ti/Al/Ni/Au ohmic contact annealed at 850 °C was prepared. It was found that after annealing at 600 °C, the sheet resistance (Rsh) of the improved device decreased to 313 Ω/□ (74.5% of that of the conventional device), and the advantage of our process on device performance was greater as the distance between ohmic contacts increased. The saturation current of the improved device was increased by approximately 23% when the distance between source and drain was 40 μm.