Abstract
Axially stacked quantum dots (QDs) in nanowires (NWs) have important applications in nanoscale quantum devices and lasers. However, there is lack of study of defect-free growth and structure optimization using the Au-free growth mode. We report a detailed study of self-catalyzed GaAsP NWs containing defect-free axial GaAs QDs (NWQDs). Sharp interfaces (1.8–3.6 nm) allow closely stack QDs with very similar structural properties. High structural quality is maintained when up to 50 GaAs QDs are placed in a single NW. The QDs maintain an emission line width of <10 meV at 140 K (comparable to the best III–V QDs, including nitrides) after having been stored in an ambient atmosphere for over 6 months and exhibit deep carrier confinement (∼90 meV) and the largest reported exciton–biexciton splitting (∼11 meV) for non-nitride III–V NWQDs. Our study provides a solid foundation to build high-performance axially stacked NWQD devices that are compatible with CMOS technologies.
Highlights
Quantum dots (QDs) have fully quantized electronic states, permitting the fabrication of high-efficiency classical and nonclassical microelectronic and optoelectronic devices.[1,2] For example, nanosized lasers can be achieved by vertically stacking a large number (e.g., 50) of homogeneous QDs.[3]
Enhanced complexity can be achived by closely stacking two or more QDs to achieve coupling/wave function entanglement.[4−6] These QD molecular systems have been proposed as novel electromagnetic resonators, quantum gates for quantum computing, and thermoelectric energy harvestors.[7−10]
Self-assembled QDs have a number of other significant disadvantages, including formation at random positions, large inhomogeneous size distributions, limited shape and size control, and restrictions on which semiconductors can be combined in a single structure
Summary
Quantum dots (QDs) have fully quantized electronic states, permitting the fabrication of high-efficiency classical and nonclassical microelectronic and optoelectronic devices.[1,2] For example, nanosized lasers can be achieved by vertically stacking a large number (e.g., 50) of homogeneous QDs.[3]. To improve the optical properties, ∼6 nm GaAs0.6P0.4 (to give 3D QD confinement), ∼18 nm Al0.5Ga0.5As0.6P0.4, and ∼9 nm GaAs0.6P0.4 shell layers were grown radially around the GaAsP core The different gradients are consistent with exciton and biexciton recombination, and the lines demonstrate the expected high power saturation Their separation is ∼11 meV, which is larger than previously reported values for non-nitride III−V QDs in an NW, for example, 6 meV for InAs QDs in GaAs NWs55 and 3 meV for GaAsP QDs in GaP NWs.[56] Possible reasons for a large exciton−biexciton separation, which is beneficial for single photon emission at elevated temperatures, and the sign of the biexciton binding energy are discussed in Supporting Information S5. NWQD quantum emitters to operate well above liquidnitrogen temperatures, which should greatly reduce device operating costs and significantly increase the range of applications
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