Field-enhanced trapping in deep levels by multiple phonon emission in semi-insulating GaAs

We have carried out the time, temperature, and illumination dependencies of the current density in a semi-insulating GaAs sample grown at 300 degreesC under strong electric field. Standard ohmic behavior was observed at room temperature. A negative differential behavior as a function of the applied electric field was observed by lowering the temperature and increasing the photon flux, and this phenomenon was associated to the field-enhanced trapp ing effect. We have fit our data with a model for enhanced capture by a mul tiple-phonon emission capture process assisted by the applied electrical fi eld. (C) 2000 American Institute of Physics. [S0021-8979(00)01822-3].