| To develop high quality AlGaN/GaN heterostructure field effect transistors (HFETs) for use in high power, high frequency, and high temperature applications, low resistance, thermal stable ohmic contacts with good surface morphology are essential. Low contact resistances have been achieved using an Au/Ti/Al/Ti contact—a minimum value of 6.33 × 10−6 Ωcm 2 was attained after annealing at 700°C for 30s. Microstructural analysis using transmission electron microscopy (TEM) indicated that there is significant interaction between the metallization components and the semiconductor during annealing. The optimum electrical properties correspond to a microstructure consisting of Au2Ti and TiAl layers as well as a thin Ti-rich layer (∼10 nm thick) at the metallization/AlGaN interface. Degradation of the contact occurred for annealing temperatures in excess of 750°C, and was accompanied by decomposition of the AlGaN layer, as well as Au2Ti and TiAl layers, and the formation of an Au-Ti-Al-Ga quaternary phase. |
