Influence of Thermal Annealing on Ohmic Contacts and Device Isolation in AIGaN/GaN Heterostructures

摘要

Gallium nitride (GaN) and related alloys (Al_xGa_(1-x)N) are promising semiconductors for high-frequency and high-power devices applications. In particular, the growth of AIGaN/GaN heterostructures on SiC substrates, due to the high thermal conductivity of SiC, can lead to significant improvement in the device performances. An important issue in the fabrication of AIGaN/GaN devices is the influence of the required thermal budget (700-900℃) on the properties of Ohmic contacts and device isolation. In this work, the influence of thermal annealing on the fabrication of AIGaN/GaN devices was studied. Ti/Al/Ni/Au multilayers led to an Ohmic behavior with a specific resistance p_c in the 10~(-5) Ωcm~2 range upon annealing between 750℃ and 850℃. The electrical behavior of Ohmic contacts was correlated with the evolution of the formed phases and with the temperature behavior of p_c. The stability of the inter-device isolation obtained by nitrogen-implantation during annealing at these temperatures was also monitored.