Conduction in illuminated GaAs/AlxGa1−xAs heterostructures. II. Calculation

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Abstract
We describe a calculation of the effects of light on the dc conduction in n‐type GaAs/AlxGa1−xAs heterojunctions. We treat the realistic case of a heterojunction with parallel conduction through both the 2D electron gas and the undepleted AlxGa1−xAs layer. We attribute persistent photoconductivity to thermally activated deep donors in the AlxGa1−xAs alloy, and we treat quantitatively the effects of continuous illumination of these deep donors. To obtain the corresponding effects on the 2D electron gas, we extend a calculation of Lee et al. [J. Appl. Phys. 5 4, 2093 (1983)]. We then combine these developments to produce for a general magnetic field state ( μB) a comprehensive model of the magnetoconductivity. This shows how varying the temperature, light intensity, magnetic field, or device parameters affects the carrier density and mobility for the heterojunction. In the companion paper [C. M. Hurd, S. P. McAlister, W. R. McKinnon, C. E. Falt, D. J. Day, C. J. Miner, and A. J. SpringThorpe, J. Appl. Phys. 6 1, 2244 (1987)], we use the model to interpret new results for GaAs/AlxGa1−xAs heterojunctions with x=0.2 and 0.3, and for Al0.3Ga0.7As alloys.