Study of recombiration-induced atomic processes associated with deep level in compound semicmductors by meano of cascade excitation spectroscopy

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Electron-hole recombination process folling pulsed electronic excitation in n-type GaP has been studied by measn of time-resolved optical techniques including absorption and luminescence measurements, photoelastic dilatation measurements and cascade excitation spectroscopy. A mid-gap luminescence band situating at 1.53 eV with a fullwidth at half maxima of 0.25 eV is induced, as well as luminescence due to donor-acceptor recombination. The mid-gap luminescence decays exponentially, indicating that it is emitted by a transition within a localized center. The formation of the state responsible for this luminescence is associated with large lattice distortion of a tenth of molecular volume, which was determined by a direct measurement of the transient volume change. The fomation yield of the center show a saturation for the excitation density of <10^(18)> <cm^(-3)> , and the estimated maximum concentration of the center is about <10^(17)> <cm^(-3)> . Thus the center is apparently related to imperfections existing in specimen prior irradiation. The result observed can only be interpreted in terms of exitsinsic self-trapped exciton.