The existence of long‐range potential fluctuations (PF) in compensated semiconductors results from the nonuniform distribution of ionized impurities, and it was observed that PF can be erased when the material is submitted to a critical field, the value of which depends on the sample. Data on the temperature and time dependence of the discharge current of a semi‐insulating GaAs crystal, which has been submitted to a critical field, are reported. The discharge current decreases with a time constant equal to the reverse of the electron emission coefficient of deep centers brought out of equilibrium by the external field. Not only the activation energy of the emission coefficient, but also the density of the deep center species responsible for the discharge current, can be determined from the data. In the case of the GaAs sample studied in this paper, the observed discharge current results from the return to equilibrium of the Cr acceptor center HL1.