Lateral p−n Junction in an Inverted InAs/GaSb Double Quantum Well

Abstract

We present transport measurements on a lateral p-n junction in an inverted InAs/GaSb double quantum well at zero and nonzero perpendicular magnetic fields. At a zero magnetic field, the junction exhibits diodelike behavior in accordance with the presence of a hybridization gap. With an increasing magnetic field, we explore the quantum Hall regime where spin-polarized edge states with the same chirality are either reflected or transmitted at the junction, whereas those of opposite chirality undergo a mixing process, leading to full equilibration along the width of the junction independent of spin. These results lay the foundations for using p-n junctions in InAs/GaSb double quantum wells to probe the transition between the topological quantum spin Hall and quantum Hall states.Diodes based on p-n junctions are one of the basic building blocks of electronic systems, with a multitude of applications including rectification, switching, signal generation and amplification, light emission, as well as photovoltaics. Advances in materials research in recent years have produced p-n junctions in a variety of novel systems such as graphene [1,2] and transition-metal dichalcogenides [3,4], an emerging class of two-dimensional semiconductors [5,6]. Beyond practical accomplishments such as downscaling, these junctions also allow us to gain new insights into fundamental physical phenomena, for example, how electron and hole edge states interact with each other in the quantum Hall (QH) regime [2,7].Here, we study the formation of a lateral p-n junction using local top gating in an inverted InAs/GaSb double quantum well (QW) heterostructure, a semiconductor system that naturally hosts both electrons and holes that are spatially separated in the vertical (growth) direction. Depending on the thicknesses of the InAs and GaSb layers, it intrinsically possesses inverted or noninverted band alignment. Furthermore, the band alignment is affected by both electric and magnetic fields, allowing for continuous tuning between the two phases [8][9][10]. In the inverted phase, coupling between the bands leads to the opening of a hybridization gap [11][12][13] hosting topologically protected helical edge states, making InAs/GaSb double QWs a two-dimensional topological insulator (TI) or quantum spin Hall (QSH) insulator [14][15][16][17][18]. Apart from the TI properties of the system, it is also of more general interest due to its complex band structure [19,20], strong spin-orbit interaction (SOI) [21][22][23], and optical properties [24].A pair of overlapping top gates enables us to independently control carrier type and density in two adjacent parts of the sample at a zero magnetic field and in the QH regime. At a zero field and when the two parts are populated by charge carriers of opposite polarity, the electrons and holes situated in their respective QWs are separated in energy by the hybridization gap responsible for the QSH insulator properties of these QWs. This gap allows the junction to function as a diode in the appropriate regimes, ...

Electron-Hole Interference in an Inverted-Band Semiconductor Bilayer

“…In the pn 0 p configuration, p-n junctions delimit the cavity. Across each junction, the density of states exhibits a local minimum as the Fermi energy transitions smoothly from below to above the hybridization gap [23]. Specifically, if a true gap exists, particles must tunnel in order to be transmitted.…”

Tunable spin-polarized edge transport in inverted quantum-well junctions

“…We stress that these results are generic for other inverted QWs displaying 2D topological insulator behavior such as InAs/GaSb. 39,40 This opens the prospect for applications of inverted QW heteropolar junctions in spintronic devices.…”

Phase slips and parity jumps in quantum oscillations of inverted InAs/GaSb quantum wells

“…Application of electric and magnetic fields offers additional tunability, allowing for continuous control of this band alignment [1][2][3]. In the inverted phase, electrons and holes hybridize, opening an energy gap [4][5][6], which facilitates the formation of the quantum spin Hall insulator (QSHI) state under the right conditions [7][8][9][10][11][12].The inverted band structure and tunability of InAs/GaSb double QWs enable many interesting experiments not directly related to the QSHI state, such as the manipulation of the SOI in single-and two-carrier regimes [13], the observation of a giant spin-orbit splitting close to the charge neutrality point (CNP) [14] and tunable mixing of quantum Hall (QH) edge states [15].Here, we report our findings on the Landau level (LL) structure in a strongly inverted InAs/GaSb double QW featuring enhanced hybridization. Using transport measurements we uncover a periodic even and odd filling of Landau levels leading to a checkerboard pattern in the longitudinal resistivity ρ xx .…”