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

We studied polycrystalline silicon grown in sheet form with oxidizing gas a dded to an inert atmosphere. It is shown that oxygen aggregates at structur al defects, preferably at grain boundaries and noncoherent twin bundles, an d to a lesser extent, also at dislocations within the grains. Oxygen agglom eration at structural defects increases their electrical activity. It is al so shown that annealings even at very low temperatures enhance the oxygen a ggregation at structural defects and consequently increase their activity. However, annealing at 450 degrees C causes dissolution of oxygen clusters m odifying the electrical properties. (C) 2000 Elsevier Science S.A. All righ ts reserved.