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

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