Evaluation of the gap state distribution in a-Si:H by SCLC measurements

In this work, the analysis of the current density–voltage (J–V) characteristics of a good-quality a-Si:H n+–i–n+ structures has been studied as a function of temperature. The defect density within the intrinsic layer of the a-Si:H n+–i–n+ structure was determined using the den Boer approach to the analysis of the space charge limited current (SCLC). The den Boer analysis yields the density of states (DOS) in only a limited part of the band gap of the sample. We emphasize that in a good-quality sample, even if it is a thin one, the den Boer approach to SCLC gives correct information about the DOS. This information comes from the states near the conduction band tail, which reside in the upper part of the gap, because of the smaller activation energy of thin samples.