Effect of thermal treatment temperature on the resistance of gold germanium films

The gold germanium thin film is an important material for the ohmic electrode of electronic devices. Vacuum thermal treatment is an important method to reduce the contact resistances for ohmic electrodes. In this paper, the relationship between the surface morphology of PVD grown Au 9 Ge 1 thin films and their resistances and temperature of vacuum thermal treatment is studied. It is found that when the vacuum thermal treatment temperature reaches 180°C, sporadic dots due to the separation of germanium atoms start to appear on the surface of the film. As temperature increased, the separation of germanium atoms gradually changes from dispersed dots to divergent snowflake shapes. And the electrical resistance of the thin film decreases. When the vacuum thermal treatment temperature reaches 265°C, the minimum resistivity of ~2.0175 Ω/mm of the gold germanium film is achieved. As the vacuum thermal treatment temperature increases further, gold atoms start to agglomerate to form hillocks, and the resistance of the films increase dramatically. The resistivity of the thin film reaches ~6.4×10 5  Ω/mm as the thermal treatment temperature reaches 280°C, which is close to power off. Compared with the sample without any thermal treatment, the temperature of vacuum thermal treatment at 265°C can reduce the resistivity of Au 9 Ge 1 film electrode by ~50%. This study provides an effective method to reduce the resistivity of gold germanium films in application of ohmic electrodes.