Capacitance-voltage characteristics were studied at various temperatures for Schottky barriers formed on n-GaAs/low-temperature-grown (LT)-GaAs/n-GaAs sandwich structures. Charge accumulation at deep traps in the LT-GaAs layer was observed. At room temperature, the C-V characteristics were found to be step-like with a wide plateau originated from emission of electrons accumulated in the LT-GaAs layer. At the temperature below 100 K, the electron emission from the LT-GaAs layer was completely suppressed. At intermediate temperatures (150-200 K), an effect of charge bistability was observed, which manifested itself as a hysteresis in the capacitance under sweeping the reverse dc bias. We suppose that the phenomenon takes place when the sweeping rate is higher than the electron emission rate but lower than the electron capture rate by the deep traps in the LT-GaAs layer.