Fabrication and characterization of a vertical pillar structure including a self-assembled quantum dot and a quantum well

We fabricate and characterize a novel vertical pillar structure including a self-assembled InAs quantum dot (QD) and an InGaAs quantum well (QW). The vertical current through both the InAs QD and an electrostatically defined QD made in the InGaAs QW can be measured by adjusting the position of the InGaAs QD in the QW plane relative to the InAs QD with two side-gate voltages applied independently. We study optical response of the current through the vertical double QD by irradiating light, which is assumed to be mainly absorbed in the InAs QDs. We successfully probe a time-dependent energy level shift due to the Coulomb interaction from holes trapped in the vicinity of the pillar.