Theory of Substitutional Deep Traps in Covalent Semiconductors

• Published in: Physical review letters 1980-03, Vol.44 (12), p.810-813
• Main Authors: Hjalmarson, Harold P., Vogl, P., Wolford, D. J., Dow, John D.
• Format: Article
• Language: English
• ISSN: 0031-9007
• DOI: 10.1103/PhysRevLett.44.810

A theory of the major chemical trends in the energies of substitutional deep traps in covalently-bonded semiconductors is presented and used to predict which elements are likely to form substitutional A1-symmetric traps with energy levels deep within the forbidden band gaps. It is assumed that the major chemical trends are determined by the energy bands of the undisturbed hosts and the atomic structures of the impurities. A simple Koster-Slater model in an orthogonalized-tight-binding-function basis with the nearest-neighbor matrix elements of the model host Hamiltonian adjusted to reproduce the known band structures is employed to obtain the eigenvalue equation for the trap energy for a substitutional defect in an unrelaxed host. Solutions to the equation are noted to define an approximately hyperbolic trap-energy function of the atomic energy difference, and imply that the deep-trap wave functions are predominantly host-like rather than impurity-like. Predicted energies of the A1-symmetric deep impurity levels as functions of impurity orbital energy are then presented for the hosts Si, Ge, GaAs, GaP, GaSb, AlAs, AlP, InAs, InP, ZnSe, and ZnTe.