Theory of anisotropic donor states in quantum-well structures.

Abstract

The s-, ${p}_{0}$-, and ${p}_{\ifmmode\pm\else\textpm\fi{}}$-like ground and excited states of anisotropic donors in quantum wells are calculated with a linear combination of Gaussian orbitals with different exponents in the z direction and xy plane. The energies and wave functions of the ground and excited states can be obtained simultaneously by this method. In the case of anisotropic donors in the bulk materials and isotropic donors in the quantum wells our results are in agreement with previous theoretical results. In some cases our results are better. Using this method we calculate the variation of the anisotropic donor energies with well widths, anisotropic factors \ensuremath{\gamma}, and impurity positions in the quantum well. The energies of s-like donor states related to the second subband are also calculated. Finally, the donors of the X band edge in Si/Si-Ge quantum wells are discussed.