Low-temperature illumination of a two-dimensional electron gas in GaAs quantum wells is known to greatly improve the quality of high-field magnetotransport. The improvement is known to occur even when the carrier density and mobility remain unchanged, but what exactly causes it remains unclear. Here, we investigate the effect of illumination on microwave photoresistance in low magnetic fields. We find that the amplitude of microwave-induced resistance oscillations grows dramatically after illumination. Dingle analysis reveals that this growth reflects a substantial increase in the single-particle (quantum) lifetime, which likely originates from the light-induced redistribution of charge enhancing the screening capability of the doping layers.
Bibliographical noteFunding Information:
We thank M. Sammon and B. Shklovskii for discussions. The work at Minnesota was supported by the NSF Award No. DMR-1309578 (measurements on sample A) and by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award No. ER 46640-SC0002567 (measurements on sample B). Sample growth at Purdue was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award No. DE-SC0006671. L.N.P. and K.W.W. of Princeton University acknowledge the Gordon and Betty Moore Foundation Grant No. GBMF 4420 and the National Science Foundation MRSEC Grant No. DMR-1420541.
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