Electronic Theory of Gettering and Passivation of Impurities in Semiconductors
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ELECTRONIC THEORY OF GETTERING AND PASSIVATION OF IMPURITIES IN SEMICONDUCTORS K.MASUDA-JINDO Department of Materials science and Engineering, Tokyo Institute of Technology, Nagatsuta, Midoriku, Yokohama 227, Japan ABSTRUCT We calculate the interaction (segregation) energies Esegr between the extended lattice defects (dislocations and grain boundaries) and impurity atoms in semiconductors by using a microscopic electronic theory. In particular, we use the tightbinding recursion method coupled to the generalized zeros-and poles method and investigate the interaction between the extended lattice defects and various kinds of the impurity atoms in semiconductors (Si). For the systematic understanding of the impurity gettering, we consider a wide variety of impurities, both sp-valence and transition metal impurities, Ti, V, Cr, Mn, Fe, Co, Ni and Cu. We will show that the variation of the gap states plays an important role in determining the interaction energy Esegr between the impurity atom and the extended lattice defects- We also discuss the passivation of the extended lattice defects by interstitial light impurities like hydrogen in Si crystal. we present a simple physical interpretation of the impurity gettering and passivation in semiconductors. INTRODUCTION Recently there has been considerable interest in the study of the impurity gettering due to the extended lattice defects such as dislocation and grain boundaries in semiconductors [1-4]. It is generally believed that dislocations trap the oversized metal atoms to minimize lattice strain, and that a similar mechanism is involved for backsealing with polycrystalline silicon and silicon nitride [3]. On the other hand, it is of considerable importance to clarify the mechanism of the passivation of the electrically active states of lattice defects by the interstitial light impurities like hydrogen. The observation of atomic hydrogen induced passivation of shallow and deep impurities in crystalline Si has led to intense interest in this area [5]. It is the purpose of the present paper to investigate the gettering and passivation of lattice defects in the covalent semiconductor Si by using the LCAO (linear combination of atomic orbitals) electronic theory [6]. We calculate the atomic configuration, impurity segregation energy and electronic states of the extended lattice defects (dislocations and grain boundaries) in Si crystal: The dopant (B, P, As, and others) and transition metal (TM) impurities (Ti, V, Cr, Mn, Fe, Co, Ni and Cu) are considered for the present calculations. Relaxations are included only for atoms which are nearest neighbours of the impurities. The relaxations for the next-nearest neighbours are found to be much smaller and are neglected. Mat. Res. Soc. Symp. Proc. Vol. 262. 01992 Materials Research Society
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2. PRINCIPLE OF CALCULATIONS To calculate the atomic configurations of the extended lattice defects (dislocations and grain boundaries), we use the LCAO recursion technique and the quenched molecular dynamics energy of the system is divi
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