US Patent 7704824 Semiconductor layer

The present invention provides a highly doped semiconductor layer. More specifically, the present invention provides a semiconductor layer that includes at least two impurities. Each impurity is introduced at a level below its respective degradation concentration. In this manner, the two or more impurities provide an additive conductivity to the semiconductor layer at a level above the conductivity possible with any one of the impurities alone, due to the detrimental effects that would be created by increasing the concentration of any one impurity beyond its degradation concentration.