Electric-Field-Effect Spin Switching with an Enhanced Number of Highly Polarized Electron and Photon Spins Using p-Doped Semiconductor Quantum Dots

Abstract

Electric-field-effect spin switching with an enhanced number of highly polarized electron and photon spins has been demonstrated using p-doped semiconductor quantum dots (QDs). Remote p-doping in InGaAs QDs tunnel-coupled with an InGaAs quantum well (QW) significantly increased the circularly polarized, thus electron-spin-polarized, photoluminescence intensity, depending on the electric-field-induced electron spin injection from the QW as a spin reservoir into the QDs. The spin polarity and polarization degree during this spin injection can be controlled by the direction and the strength of the electric field, where the spin direction can be reversed by excess electron spin injection into the QDs via spin scattering at the QD excited states. We found that the maximum degrees of both parallel and antiparallel spin polarization to the initial spin direction in the QW can be enhanced by p-doping. The doped holes without spin polarization can effectively contribute to this electric-field-effect spin switching after the initial electron spin injection selectively removes the parallel hole spins. The optimized p-doping induces fast spin reversals at the QD excited states with a moderate electric-field application, resulting in an efficient electric-field-driven antiparallel spin injection into the QD ground state. Further excess hole doping prevents this efficient spin reversal due to multiple electron−hole spin scattering, in addition to a spin-state filling effect at the QD excited states, during the spin injection from the QW into the QDs.

Room-temperature electric field control of spin filtering efficiency for enhanced modulation of optical spin polarization in a defect-functional 0D–2D hybrid nanostructure

“…As described above, a clear difference in the PL intensity appears when changing the bias voltage between 0.2 V and −2 V. The bias-voltage dependence of the QD PL intensity has been previously discussed based on the electric-field-dependent absence of electrons or holes inside the QDs. 25–27 It should be noted that there was also a significant difference in the PL polarization over a wide energy range. Fig.…”

“…23,24 The circular polarization degree of photoluminescence (PL), corresponding to the spin polarization degree of electrons, has been controlled by an electric field using InGaAs QW-QD tunnel-coupled structures. 25,26 Efficient RT voltage control of PL circular polarization in the range of 3-15% has recently been demonstrated. 27 However, for such an InGaAs-based nanostructure, the PL intensity decreases significantly at RT because of the dominant thermal escape of electrons from the QDs to the barrier.…”

Efficient Room‐Temperature Voltage Control of Picosecond Optical Spin Orientation Using a III‐V Semiconductor Nanostructure

“…[29] In addition, the QW behaves as a reservoir of electrons or holes, depending on the applied bias voltage. [25,26] The number ratio of electrons to holes injected into the QDs can be precisely controlled through the electricfield direction and strength.…”

“…The electric field effects on spin polarity and its polarization degree have been explored in III‐V semiconductor QDs via circularly polarized PL at low temperatures. [ 22–26 ] A significant negative PL polarization, corresponding to the spins antiparallel to the initial spin direction, has been observed at a specific bias voltage. The PL polarization can be manipulated from −20% to +10% by changing the bias voltage (Figure 1b).…”

Numerical Modeling and Performance Evaluation of SnS Based Heterojunction Solar Cell with p+ SnS BSF Layer

“…Adding another layer to create an electric eld near to the back contact will help to reduce the surface recombination process. To generate the strong electric eld, heavily doped semiconductor layer can be added at the rear end to improve the e ciency [ 14 ]. Till now, few researchers have studied theoretically the impact of adding a highly doped layer near the back contact of CdTe, CZTS, CZTSe, CIGS, Sb 2 S 3 based solar cells [ 15 ][ 16 ].…”