STRUCTURE OF THE DX STATE FORMED BY DONORS IN (AL,GA)AS AND GA(AS,P)

High-resolution Laplace-transform deep level transient spectroscopy has been used to study the influence of the defect local environment on electron emission from the DX centers related to group-IV (silicon) donors in AlxGa1-xAs (0.20 < x < 0.76) and delta-doped GaAs and group-VI (tellurium) donor elements in AlxGa1-xAs (0.25 < x < 0.73) and GaAs0.35P0.65. The experimental evidence that substitutional-interstitial atom motion is responsible for DX behavior and for the associated metastability effects is presented. The atom which is subjected to this transition is for DX(Si) silicon itself, as in the spectra only one group of peaks in AlxGa1-xAs is observed, while for DX(Te) it can be either gallium or aluminum, producing two groups of peaks in AlxGa1-xAs and three or four broad emission bands in GaAs0.35P0.65. The present results rule out a possibility that the DX-type defect states are formed by a donor atom in a stable substitutional position with a small lattice relaxation or with a fully symmetric large lattice relaxation effect. (C) 1995 American Institute of Physics.