HOPPING CONDUCTION AND ITS PHOTOQUENCHING IN MOLECULAR-BEAM EPITAXIALGAAS GROWN AT LOW-TEMPERATURES

As the growth temperature of molecular beam epitaxial GaAs is increase d from 250 to 400 degrees C, the dominant conduction changes from hopp ing conduction to band conduction with a donor activation energy of 0. 65 eV. A 300 degrees C grown layer is especially interesting because e ach conduction mechanism is dominant in a particular temperature range , hopping below 300K and band conduction above. Below 140K, the hoppin g conduction is greatly diminished (quenched) by irradiation with eith er infrared (hv less than or equal to 1.12 eV) or 1.46 eV light, but t hen recovers above 140K with exactly the same thermal kinetics as are found for the famous EL2. Thus, the 0.65 eV donor, which is responsibl e for both the hopping and band conduction, is very similar to EL2, bu t not identical because of the different activation energy (0.65 eV vs 0.75 eV for EL2).