Oxygen-related deep levels in oxygen doped EFG poly-Si

We studied polycrystalline silicon grown in sheet form with oxidizing gas added to an inert atmosphere. It is shown that oxygen aggregates at structural defects, preferably at grain boundaries and noncoherent twin bundles, and to a lesser extent, also at dislocations within the grains. Oxygen agglomeration at structural defects increases their electrical activity. It is also shown that annealings even at very low temperatures enhance the oxygen aggregation at structural defects and consequently increase their activity. However, annealing at 450°C causes dissolution of oxygen clusters modifying the electrical properties.