Temperature dependence of the Hall-effect electron concentration in n-Al0.28Ga0.72 As/GaAs heterostructures

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Abstract
A precise model for calculation of the spatial distribution of electrons in n‐(Al,Ga)As/GaAs heterostructures is described. The model has been used to investigate the spatial distribution of electrons in a n‐Al0.28Ga0.72 As/GaAs structure as a function of temperature. The results were compared with Hall‐effect experiments on heterostructures as well as thick Al0.28Ga0.72 As films grown by molecular‐beam epitaxy (MBE). For both types of samples it was found that it was necessary to use either a conduction‐band density of states which is much higher than expected from literature data or to use a temperature‐dependent activation energy. The slight increase in concentration of the two‐dimensional electron gas observed for lower temperatures could be attributed to a sharpening of the transition region between high‐ and low‐ionization degrees in the depletion layer close to the interface. It thus indicates that the Hall factor changes very little as expected for a degenerate electron system.