Dresden 2017 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 74: Group IV: Si/Ge/SiC
HL 74.2: Talk
Thursday, March 23, 2017, 12:15–12:30, POT 06
Modulation Doping of Si using Al-induced Acceptor States in SiO2 — Dirk König1, •Daniel Hiller2, Sebastian Gutsch2, Margit Zacharias2, and Sean Smith1 — 1University of New South Wales (UNSW), Sydney, Australia — 2Laboratory for Nanotechnology, IMTEK, University of Freiburg, Germany
Silicon nanovolumes suffer from effects that impede conventional doping due to fundamental physical principles such as out-diffusion, statistics of small numbers, quantum- or dielectric confinement. Efficient and reliable control over the majority charge carriers by impurity doping is infeasible for ultra-small Si crystals [1].
In this work, we demonstrate a heterostructure modulation doping method for Si, similar to the concept of modulation doping originally invented for III-V semiconductors [2]. Our approach utilizes a specific acceptor state of Al-atoms in SiO2, which is located 0.5 eV below the Si valence band, to generate holes as majority carriers in adjacent Si [3]. The relocation of the impurity dopants from Si to SiO2 circumvents all nanoscale doping problems. We present successful Si modulation doping from the theoretical background (density functional theory simulations, DFT) to experimental evidence by capacitance-voltage (C-V), Hall-measurements and deep level transient spectroscopy (DLTS). In addition, we demonstrate how modulation doping of bulk-Si enables passivating hole selective tunnelling contacts as required for high-efficiency photovoltaics [3].
[1] Sci. Rep. 5, 09702 (2015) [2] Appl. Phys. Lett. 33, 665 (1978) [3] D. König & D. Hiller et al., Sci. Rep., under review (2016)