Observation of negative persistent photoconductivity in an n-channel GaAs/AlxGa1−xAs single heterojunction

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Abstract
We report the first observation of negative persistent photoconductivity at 4.2 K in an n‐channel modulation doped GaAs/Al0.33Ga0.67As single heterostructure, where two‐dimensional electrons have a mobility of ∼550 000 cm2/V s when density is ∼3.0×1011 cm−2. Based on extensive magnetotransport measurements, we conclude that the negative persistent photoconductivity effect comes from the time dependence of (1) the annihilation of two‐dimensional electrons by photoexcited holes, and (2) the trapping and de‐trapping of photoexcited electrons by shallow donors in doped Al0.33Ga0.67As. A model that quantitatively explains the nonexponential recovery time is presented.