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(a) SEM micrograph of four Schottky metallic gates precisely positioned around an InP pyramidal nanotemplate used to control the QD nucleation site. (b) Schematic view of device indicating a single InAs QD embedded in the intrinsic region (InP) of an Schottky diode. A 20 nm layer of is used between the top Schottky gates and -doped InP substrate to minimize leakage current. (c) Typical single-dot PL from device structure shown in (a), which emits around 830 meV (1500 nm).
Typical PL spectra for an individual, prepositioned InAs/InP QD as a function of vertical electric field (reverse bias). Single electron control is demonstrated by discrete changes in the optical spectra. For this particular dot, the electron number can be tuned from a QD containing two electrostatically induced electrons to an empty dot, where the PL probes only that of . The intensity of the lower emission peak is multiplied by a factor of three.
Stark shift of (black squares) and (blue circles) as a function of vertical electric field. Here, the is offset by a constant energy. From a quadratic fit of the data (solid black line), the built-in dipole and Stark shift are obtained. The size and direction of the built-in dipole indicate that the InAs QD composition is uniform.
Fine structure at fixed bias for , , and , respectively. The FSS of is and of is , while no detectable FSS is observed for as expected.
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