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Register a new userSpin-orbit effects in the hydrogenic impurity levels of wurtzite semiconductors
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Pablo I. Tamborenea
Publication date
2019
fields
Physics
and research's language is
English
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The corrections to the $E_2^*$ energy level of hydrogenic impurities in semiconductors with wurtzite crystal structure are calculated using first-order perturbation theory in the envelope-function approximation. We consider the intrinsic (Dresselhaus) spin-orbit effective Hamiltonian in the conduction band and compare its effects to the renormalized extrinsic (Rashba) spin-orbit interaction which is analogous to the spin-orbit interaction in the bare hydrogen atom. In order to evaluate the extrinsic spin-orbit interaction we obtain the renormalized coupling constant $lambda^*$ for wurtzite semiconductors from 8-band Kane theory. We apply our theory to four representative binary semiconductors with wurtzite crystal structure, namely, GaN, ZnO, InN and AlN, and discuss the relative strength of the effects of the intrinsic and extrinsic spin-orbit contributions.
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The response of semiconductor materials to external magnetic fields is a reliable approach to probe intrinsic electronic and spin-dependent properties. In this study, we investigate the common Zeeman splitting features of novel wurtzite materials, namely InP, InAs, and GaAs. We present values for the effective g-factors of different energy bands and show that spin-orbit coupling effects, responsible for the spin splittings, also have noticeable contributions to the g-factors. Within the Landau level picture, we show that the nonlinear Zeeman splitting recently explained in magneto photoluminescence experiments for InP nanowires by Tedeschi et al. [Phys. Rev. B 99, 161204 (2019)] are also present in InAs, GaAs and even in the conventional GaN. Such nonlinear features stem from the peculiar coupling of the A and B valence bands, as a consequence of the interplay between the wurtzite crystal symmetry and the breaking of time-reversal symmetry by the external magnetic field. Moreover, we develop an analytical model to describe the experimental nonlinear Zeeman splitting and apply it to InP and GaAs data. Extrapolating our fitted results, we found that the Zeeman splitting of InP reaches a maximum value, which is a prediction that could be probed at higher magnetic fields.
Millikelvin magnetotransport studies are carried out on heavily $n$-doped wurtzite GaN:Si films grown on semi-insulating GaN:Mn buffer layers by metal-organic vapor phase epitaxy. The dependency of the conductivity on magnetic field and temperature is interpreted in terms of theories that take into account disorder-induced quantum interference of one-electron and many-electron self-crossing trajectories. The Rashba parameter $alpha_{text{R}},=,(4.5 pm 1)$ meV$AA$ is determined, and it is shown that in the previous studies of electrons adjacent to GaN/(Al,Ga)N interfaces, bulk inversion asymmetry was dominant over structural inversion asymmetry. The comparison of experimental and theoretical values of $alpha_{text{R}}$ across a series of wurtzite semiconductors is presented as a test of current relativistic ab initio computation schemes. It is found that electron-electron scattering with small energy transfer accounts for low temperature decoherence in these systems.
The doping of semiconductors with magnetic impurities gives rise not only to a spin-spin interaction between quasi-free carriers and magnetic impurities, but also to a local spin-independent disorder potential for the carriers. Based on a quantum kinetic theory for the carrier and impurity density matrices as well as the magnetic and non-magnetic carrier-impurity correlations, the influence of the non-magnetic scattering potential on the spin dynamics in DMS after optical excitation with circularly polarized light is investigated using the example of Mn-doped CdTe. It is shown that non-Markovian effects, which are predicted in calculations where only the magnetic carrier-impurity interaction is accounted for, can be strongly suppressed in the presence of non-magnetic impurity scattering. This effect can be traced back to a significant redistribution of carriers in $mathbf{k}$-space which is enabled by the build-up of large carrier-impurity correlation energies. A comparison with the Markov limit of the quantum kinetic theory shows that, in the presence of an external magnetic field parallel to the initial carrier polarization, the asymptotic value of the spin polarization at long times is significantly different in the quantum kinetic and the Markovian calculations. This effect can also be attributed to the formation of strong correlations which invalidates the semiclassical Markovian picture and it is stronger when the non-magnetic carrier-impurity interaction is accounted for. In an external magnetic field perpendicular to the initial carrier spin, the correlations are also responsible for a renormalization of the carrier spin precession frequency.
We show that the spin-orbit interaction (SOI) produced by the Coulomb fields of charged impurities provides an efficient mechanism for the bound states formation. The mechanism can be realized in 2D materials with sufficiently strong Rashba SOI provided that the impurity locally breaks the structure inversion symmetry in the direction normal to the layer.
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