Type-I-type-II hybrid quantum well with tunable hole g-factor

Type-I-type-II hybrid quantum well with tunable hole g-factor
g-factor; hybrid quantum well; spin state; quantum computation
Issue Date
, P2-251
In this research, we theoretically investigate the electrical manipulation of hole g-factor by switching the band alignments (type-I and type-II) of a hybrid quantum well (QW). The structures we considered are composed of two separate QWs, made out of compressively strained layer and tensile strained layer: e.g., InAsP-GaAs layers embedded in InP matrix (Fig. 1(a)), InGaP-GaP layers embedded in AlAs matrix (Fig. 1(b)) The ground heavy-hole (HH) state (localized in the compressively strained layer) and the light-hole (LH) state (localized in the tensile strained layer) of the hybrid QW are designed to be degenerate in energy by an appropriate choice of the compositions and widths of the layers. Figure 1 shows the band alignments and electron(CB), HH, and LHstateswavefunctions of InAs0.58P0.42-GaAs/InP, and In0.6Ga0.4P-GaP/AlAs structures calculated by an eight-band k·p method. The transitions between the CB and HH states exhibit type-I character, while those between the CB and LH states show type-II character. The spatial separation between the CB (and HH) and LH states are controlled by varying the thickness of AlInP barrier between the two layers. We plot the hole band dispersion relation of InGaP-GaP/AlAs QW in Fig. 2. The hole ground state exhibits a negative effective mass due to the strong coupling between the subbands. The degeneracy between the HH and LH states at the zone center is removed at finite inplane wave vector, and the twofold spin degeneracy is slightly lifted by the lack of structural inversion symmetry [1]. An external electric field lifts the degeneracy between the HH and LH states at the zone center, and enables the switching between the type-I and type-II band alignments (Fig. 3). Since the g-factor and the cyclotron effective mass strongly depend on the well materials and the hole characters (i.e. HH/LH), the structure allows us to electrically modulate the g-factor.
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