Electric-field inversion asymmetry: Rashba and Stark effects for holes in resonant tunneling devices

Abstract

We report experimental evidence of excitonic spin-splitting, in addition to the conventional Zeeman effect, produced by a combination of the Rashba spin-orbit interaction, Stark shift and charge screening. The electric-field-induced modulation of the spin-splitting are studied during the charging and discharging processes of p-type GaAs/AlAs double barrier resonant tunneling diodes (RTD) under applied bias and magnetic field. The abrupt changes in the photoluminescence, with the applied bias, provide information of the charge accumulation effects on the device.The effect of the spin-orbit (SO) interaction in quasitwo-dimensional (Q2D) systems has attracted renewed attention in recent years. The topic has been on the focus of many optical and transport investigations of spin-related phenomena in nanoscopic systems [1,2,3], a subject of great fundamental and technological interest [4,5,6,7]. In this letter, we address experimental evidence of electric field coupling to the spin degree of freedom of carriers in RTD; here in particular, the prevailing influence can be attributed to the SO and Stark effects on the hole electronic structure. These interactions are relevant to the study of the internal electric fields and the charge accumulation in the structure. The simultaneous investigation of optical and transport properties at high magnetic and electric parallel fields, has permitted a thorough characterization of the main processes involved in the system response. The novelty of this result consists of the optical detection of electric field modulation of the effective spin-splitting beyond the Zeeman effect and its unambiguous correlation to the transport mechanisms which is responsible for the charge buildup in the states of the RTD.This study is carried out on a symmetric p − i − p GaAs/AlAs RTD, that has been previously used to characterize hole space charge buildup and resonant effects in a magnetic field [8]. The structure is in the form of a 400µm diameter mesa with a metallic AuGe annular top contact to allow optical access. The diode was mounted in a superconducting magnet and the emission spectra were recorded using a double spectrometer coupled to a CCD system with polarizer facilities to select left (right) σ +(−) configurations. When light from an Ar + laser is focused close to the surface, minority electrons are created [8]. As the bias approaches a resonant condition, the carrier density inside the QW increases and then decreases, resulting in the negative differential resistance (NDR) region when the resonance is traversed. The photo-generated electrons tunneling into the QW layer can recombine with the injected holes or tunnel out of the well layer. These processes are represented schematically in the Fig. 1 (a).The I − V characteristics, shown in Fig. 1 (b), displays a series of peaks associated with the injected holes (I dark ) from the hole accumulation layer formed in the outside interface of the diode (see Fig. 1 (a)). Under illumination, an increase of current is observed (I light ) due to ...

Voltage- and Light-Controlled Spin Properties of a Two-Dimensional Hole Gas in p-Type GaAs/AlAs Resonant Tunneling Diodes

“…However, our experimental results must be attributed to the electric field-induced coupling of the hole spin degree of freedom, the Rashba spin orbit and Stark effects on the whole electronic structure. 15 …”

“…10,11 Furthermore, resonant tunneling diodes (RTDs) are interesting devices for studying the physical properties of 2D systems due to the fact that their carrier density and the resulting parameters, such as the filling factor, can be varied by the applied bias voltage. [12][13][14][15][16][17][18][19][20][21] Several previous works have shown that 2DHG formed in the accumulation layer can inject spin-polarized holes in the quantum well (QW) region and make an important contribution to the spin polarization of carriers in resonant tunneling diodes. 21 In this paper, we have investigated the effect of the electric field and laser excitation intensity on the spin properties of 2DHGs formed at the accumulation layer next to the emitter barrier of a ptype GaAs/AlAs resonant tunneling diode.…”

Nanothermometer Based on Resonant Tunneling Diodes: From Cryogenic to Room Temperatures

“…The current I depends on the transmission probability and the electron supply function, 16,17 while the RTD voltage drop, V rtd , is mainly determined by the arrangement of accumulated electron and ionized donor densities. 18 Two electron densities, n ac and n i , are formed due …”

Spin Polarization of Carriers in InGaAs Self-Assembled Quantum Rings Inserted in GaAs-AlGaAs Resonant Tunneling Devices

“…Resonant tunneling diodes (RTDs) have also been a research focus for many years [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] . Several works investigated their fundamental physical properties and possible potential applications in spintronics [8][9][10][11][12][13][14][15][16][17] .…”

“…Several works investigated their fundamental physical properties and possible potential applications in spintronics [8][9][10][11][12][13][14][15][16][17] . For example, it was shown that spin polarization of carriers in RTDs can be voltage and light dependent under magnetic field [8][9][10] .…”