Two-Dimensional Giant Tunable Rashba Semiconductors with Two-Atom-Thick Buckled Honeycomb Structure

Abstract

Spin field-effect transistors (SFETs) based on the Rashba effect could manipulate the spin of electrons electrically, while seeking desirable Rashba semiconductors with large Rashba constant and strong electric-field response, to preserve spin coherence remains a key challenge. Herein, we propose a series of 2D Rashba semiconductors with two-atom-thick buckled honeycomb structure (BHS) according to high-throughput first-principles density functional theory calculations. BHS semiconductors show large Rashba constants that are favorable to be integrated into nanodevices superior to conventional bulk materials, and they can be fabricated by mechanical exfoliation or chemical vapor deposition. In particular, 2D AlBi monolayer has the largest Rashba constant (2.77 eVÅ) of all 2D Rashba materials. Furthermore, 2D BiSb monolayer is a promising candidate for SFETs due to its large Rashba constant (1.94 eVÅ) and strong electric field response (0.92 eÅ2). Our designed 2D-BiSb-SFET shows shorter spin channel length (42 nm with strain) than conventional SFETs (2–5 μm).

Spin–Orbit Coupling in 2D Semiconductors: A Theoretical Perspective

“…Further research by Bychkov and Rashba demonstrated that the Rashba effect also occurs in quasi-2D systems . Over the past few decades, the Rashba effect and Dresselhaus effect have been observed in various systems, such as 2D semiconductors, heterostructures, metal surfaces, 3D bulk materials, and quantum wells. ,,− …”

“…In 2D electron gas systems with C 2 v symmetry, the Rashba Hamiltonian can be represented as where α is the Rashba constant denoting the strength of the Rashba effect, and z ̂ is the surface normal. This Rashba Hamiltonian can apply to most 2D semiconductors. − Corresponding eigenvalues and eigenstates are where the symbol + (−) denotes the inner (outer) branch, and energy difference E R and momentum offset k R can be measured in the DFT band structures as shown in Figure d. The Rashba constant α is calculated by …”

“…Furthermore, Rashba states should locate in the valence band maximum (VBM) or conduction band minimum (CBM) for practical applications. In this section, we summarize a series of 2D Rashba semiconductors theoretically, including AB binary buckled monolayers, − Janus monolayers (especially for MXY Janus monolayers), − 2D perovskites, ,− and so on. As for 2D Dresselhaus semiconductors, although we have summarized the linear Dresselhaus Hamiltonian of 2D electron gas systems theoretically, there are no 2D semiconductors that demonstrate the pure Dresselhaus effect theoretically and experimentally, where “the pure Dresselhaus effect” means the absence of the Rashba effect.…”

“…As for groups IV–VI, calculated Rashba constants of the CBM at the Γ point for three MTe monolayers (M = Ge, Sn, Pb) are 0.60, 0.62, and 0.60 eV·Å, respectively . Moreover, the Rashba effect for 127 buckled binary hexagonal monolayers from group III to group VII has been systematically investigated recently . Ten 2D binary hexagonal semiconductors (BiB, AlBi, GaSb, InSb, TlP, PbSi, BiN, BiP, BiAs, and BiSb) have giant Rashba constants larger than 1.0 eV·Å.…”

Two-dimensional InSb/GaAs- and InSb/InP-based tandem photovoltaic device with matched bandgap

“…20–22 Although the PCEs of 2D material-based SCs can be up to about 20%, 23,24 this is still below the S–Q limit. Furthermore, we find that 2D semiconductors possess tunable E g and higher carrier mobilities, 25–29 which will hopefully fulfill the requirements of tandem PVs. Taking the successful application of Si-based tandem PVs into account, therefore, our target is to search for a bottom-cell semiconductor approaching the E g of Si with the E g of the top-cell semiconductor matching the bottom material.…”