A. M. Burke, D. Waddington, D. Carrad, R. Lyttleton, H. H. Tan, P. J. Reece, O. Klochan, A. R. Hamilton, A. Rai, D. Reuter, A. D. Wieck, A. P. Micolich
Gate instability/hysteresis in modulation-doped p-type AlGaAs/GaAs heterostructures impedes the development of nanoscale hole devices, which are of interest for topics from quantum computing to novel spin physics. We present an extended study conducted using custom-grown, matched modulation-doped n-type and p-type heterostructures, with/without insulated gates, aimed at understanding the origin of the hysteresis. We show the hysteresis is not due to the inherent `leakiness' of gates on p-type heterostructures, as commonly believed. Instead, hysteresis arises from a combination of GaAs surface-state trapping and charge migration in the doping layer. Our results provide insights into the physics of Si acceptors in AlGaAs/GaAs heterostructures, including widely-debated acceptor complexes such as Si-X. We propose methods for mitigating the gate hysteresis, including poisoning the modulation-doping layer with deep-trapping centers (e.g., by co-doping with transition metal species), and replacing the Schottky gates with degenerately-doped semiconductor gates to screen the conducting channel from GaAs surface-states.
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http://arxiv.org/abs/1207.2851
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