Speaker
Description
Carrier density-dependent mobility in semiconductor nanostructures
*Christian E. N. Petersen1, Damon J. Carrad1,2, Thierry D. Pomar2, Daria V. Beznasyuk1,3, Jung-Hyun Kang1,3, Gunjan Nagda1,3, Dennis Valbjørn Christensen2, Peter Krogstrup1,3 and Thomas S. Jespersen1,2
1. Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, Denmark
2. Department of Energy Conversion and Storage, Technical University of Denmark, Denmark
3. Microsoft Quantum Materials Lab Copenhagen, Denmark
* Contact: lbc622@alumni.ku.dk
Increasing material quality and carrier mobility of semiconductor nanostructures is crucial in many applications for coherent nanoelectronics and nanotechnology. A challenge in this respect is the inherent difficulty in performing four-terminal Hall effect measurements on nanostructures, including nanowires [1] and prompts efforts to extract mobility in other ways. In materials where mobility is independent of carrier density, field-effect measurements can be used [2]. However, this situation seldom occurs in nanostructures, where density-dependent scattering mechanisms give rise to a non-constant – and in some cases non-monotonic – relationship between carrier mobility and density. In this study, we investigate the non-monotonous electron mobility in InAs nanowires in a Hall bar geometry made using selective area growth [3,4]. We develop a method to accurately extract the gate voltage-dependent mobility from two-terminal field-effect transistor measurements and demonstrate an excellent match with the Hall mobility. Our method enables extracting similar information to a Hall effect measurement on two-terminal devices at zero magnetic field. Going beyond the conventional models which assume constant mobility – and significantly overestimate the true value - our approach further enables systematic investigation of the underlying scattering mechanisms that determine the mobility in a particular carrier density regime. For example, our devices exhibited an initial rise in mobility with increasing gate voltage, followed by a fall beyond the peak around Vtg = 0.5 V. The two behaviours may be attributed to screening of charged impurities and inter-subband scattering, respectively [5].
[1] K. Storm, et al., Nat Nano 7, 718–722 (2012)
[2] S. M. Sze, Physics of Semiconductor Devices, 3rd ed. Hoboken, N.J: Wiley-Interscience (2007)
[3] F. Krizek et al., Phys. Rev. Materials 2, 093401 (2018)
[4] D. V. Beznasyuk et al., arXiv:2103.15971 (2021)
[5] S. Ahn et al., arXiv:2109.00007 (2021)
| Field of study | Quantum Physics |
|---|---|
| Supervisor | Jesper Nygård |
