Electronic structures in single pair of InAs∕GaAs coupled quantum dots with various interdot spacings

Abstract

The electronic structures in a single pair of InAs/ GaAs coupled quantum dots ͑CQDs͒ with various interdot spacings are investigated by performing photoluminescence ͑PL͒ and photoluminescence excitation ͑PLE͒ measurements. Luminescence from the bonding ͑X + ͒ and antibonding ͑X − ͒ states caused by electron-wave-function coupling was observed in the micro-PL spectra of the CQDs. We indicate the contribution of the hole excited states to the PL spectra in QDs based on the results for the spectral dependence on circularly polarized light and the structures of PLE spectra. PLE spectra reveal the electronic structures of the CQD system at higher energy states where both the common excited levels due to the level sharing between the electron excited states and the individual excited levels related to the hole excited states coexist. In addition, we mention that the energy-level mixing due to the strong-wave-function coupling between two QDs influences the decoherence of the carrier relaxation processes.

Energy Transfer within Ultralow Density Twin InAs Quantum Dots Grown by Droplet Epitaxy

“…A well-developed technique to fabricate such QDM is the epitaxial growth of a vertically aligned QD pair, 10Ϫ12 in which the coupling between two QDs can be tuned by the spacer thickness and external fields. 13,14 Another approach to obtain QDMs is to fabricate a laterally coupled QD pair. Since self-assembled QDs are typically characterized by a flat geometry, the nature of the lateral coupling may differ appreciably from that of vertical coupling, rendering the study of laterally coupled QDMs of fundamental interest.…”

“…Self-assembled semiconductor quantum dots (QDs) are the subject of increasing interest due to their potential in developing a new generation of optoelectronic devices. − As an example, a group of closely spaced QDs can act as a “QD molecule” (QDM), which is interesting, both as a new playground for studying interacting electronic systems and as a building block to perform complex quantum computing operations. − The simplest QDM is composed of two interacting QDs. A well-developed technique to fabricate such QDM is the epitaxial growth of a vertically aligned QD pair, − in which the coupling between two QDs can be tuned by the spacer thickness and external fields. , Another approach to obtain QDMs is to fabricate a laterally coupled QD pair. Since self-assembled QDs are typically characterized by a flat geometry, the nature of the lateral coupling may differ appreciably from that of vertical coupling, rendering the study of laterally coupled QDMs of fundamental interest. , However, the stochastic nature of self-assembly growth results in the random distribution of InAs QDs on GaAs surfaces, presenting an obstacle for fabrication of laterally coupled QDMs.…”

Probing the band structure of InAs∕GaAs quantum dots by capacitance-voltage and photoluminescence spectroscopy

“…Some experimental work has also been done to understand the electronic structure of QDs by using photoluminescence ͑PL͒ and PL excitation spectroscopy, photocurrent spectroscopy, capacitance-voltage ͑C-V͒ spectroscopy, absorption spectroscopy, and related techniques. [6][7][8][9][10][11][12] Regarding the use of C-V spectroscopy to determine absolute energy scales, it is a problem to determine the Schottky barrier formed on the sample surface, which varies from sample to sample. One way to extract the Schottky barrier is to fabricate several devices with different lever arms or to grow a reference sample in which no QD layer is present.…”

Terahertz Lasing at Roomtemperature: Numerical Study of a Vertical-Emitting Quantum Cascade Laser Based on a Quantum Dot Superlattice

“…For the bandstructure presented in Fig. 3, we assumed In 0.7 Ga 0.3 As QDs with a side-wall inclination of 40 • , a basis length of 14.7 nm and a height of 2.8 nm, in agreement with reports in [33][34][35][36]. The vertical aspect ratio (height divided by base diameter) of AR v = 0.135 is chosen slightly lower to account for material interdiffusion found in experiment.…”