The origin of the minority impurity states in heavily doped semiconductors

The influence is examined of growth conditions of heavily doped n-type semiconductors on the width and energy position of Gaussian-shape impurity band where non-equilibrium holes are localized. The energy levels of the impurity band are shown to be caused by associations of oppositely charged crystal imperfections (so-called associates) including several shallow donor impurity atoms and a deep structural defect. The reason of Gaussian broadening of these states is a random spatial arrangement of associated imperfections about each other within a given associate. (author)