Abstract
Understanding the detailed electronic structure of deep defect states in narrow band-gap semiconductors has been a challenging problem. Recently, self-consistent ab initio calculations within density functional theory using supercell models have been successful in tackling this problem. In this paper, we carry out such calculations in PbTe, a well-known narrow band-gap semiconductor, for a large class of defects: cationic and anionic substitutional impurities of different valence, and cationic and anionic vacancies. For the cationic defects, we study the chemical trends in the position of defect levels by looking at series of compounds , where is vacancy or monovalent, divalent, or trivalent atom. Similarly, for anionic defects, we study compounds , where is vacancy, S, Se or I. We find that the density of states near the top of the valence band and the bottom of the conduction band get significantly modified for most of these defects. This suggests that the transport properties of PbTe in the presence of impurities may not always be interpreted by simple carrier doping (from bound impurity states in the gap) concepts, confirming such ideas developed from qualitative and semiquantitative arguments.
- Received 17 May 2006
DOI:https://doi.org/10.1103/PhysRevB.74.155205
©2006 American Physical Society