PHOTOIONIZATION OF GE--DX STATE IN GAAS

We have determined the efficiency of photoionization of Ge--DX state i n GaAs as a function of photon energy. The optical ionization energy d erived from the fitting is about 1.0 eV. It proves a large difference between optical and thermal ionization energies and confirms that for Ge-impurity, the broken-bond model and large lattice relaxation are va lid and not the breathing mode with small lattice relaxation, resultin g from the calculations presented for Ge-impurity in T.M. Schmidt, A. Fazzio, M.J. Caldas, Mater. Sci. Forum 196/201, 273 (1995). PACS numbe rs: 63.20.Mt, 71.55.-i, 72.40.+w.