In the presence of impurities or in a nonstoichiometric solid, free electrons or electron holes are produced as a result of “charge compensation” to neutralize the effect of charged ionic defects 。

在杂质存在的情况下，或在非化学计量比的固体中，为了中和带电离子缺陷所引起的电荷不平衡，便会产生自由电子或电子空穴。