Reverse bias annealing of Schottky diodes: Evidence for the lower defect density and better stability of polymorphous silicon compared to amorphous silicon

Reverse bias annealing (RBA) experiments on high quality Schottky diodes formed on both hydrogenated amorphous silicon (a-Si:H) and hydrogenated polymorphous silicon (pm-Si:H) are presented. A strong increase of the deep defect density after RBA is revealed by capacitance measurements. The spatial location of created defects is shown to be limited within the space charge region established by the reverse bias applied during annealing. Changes are metastable and the structure can recover after annealing under short circuit. It is shown that pm-Si:H has a much lower deep defect density and is more robust against defect creation than a-Si:H. Results are discussed in terms of possible mechanisms for defect creation related to the microstructure of the materials.