Low-temperature crystallization of hydrogenated amorphous silicon films in contact with evaporated aluminum electrodes

Measurements are reported on x-ray diffraction and Auger electron spectroscopy studies of Al films on phosphorous-doped hydrogenated amorphous silicon (a-Si:H) prepared by rf glow discharge deposition. Infrared absorption and current-voltage characteristics of and Al electrode a-Si:H p-i-n diodes are also presented. Si and Al Auger depth profile data show that Si was detected at the free surface of the 5000-Å Al film on the 1500-Å a-Si:H film after a 185 °C anneal, while a constant Si signal was detected in the Al film from its free surface to the interface with the a-Si:H after a 200 °C anneal. The 200 °C anneal reduced the p-i-n diodes to resistors. The a-Si-H in contact with the Al film crystallized at 300 °C. A 360 °C anneal prior to the Al deposition raised the recrystallization temperature above 300 °C. The evolution of hydrogen is proposed as a mechanism for lowering the recrystallization temperature in a–Si:H.