Aluminum-induced crystallization and counter-doping of phosphorous-doped hydrogenated amorphous silicon at low temperatures

Aluminum metal-induced crystallization and doping of hydrogenated amorphous silicon (a-Si:H) have been investigated. Aluminum was evaporated onto device quality a-Si:H films deposited in an ultrahigh vacuum plasma-enhanced chemical vapor deposition system. These Al/a-Si:H structures were annealed in the 100–300 °C range. Electrical, surface morphological, and chemical characterizations of the material were performed. The transmission line model technique was used for electrical characterization. Raman spectroscopy showed that crystallization of the interacted a-Si:H film underneath Al pads initiates at temperatures as low as 180 °C. X-ray diffraction analysis showed very good polycrystallinity of the interacted film. Electrical measurement, Hall measurement and x-ray photoelectron spectroscopy analysis results revealed that a-Si:H film in contact with Al becomes heavily doped by Al during crystallization as a result of annealing at relatively low temperatures.