Exciton fine structure in interfacial quantum dots

Abstract

We have studied, by 'micro-magneto-photoluminescence', the eigenstates of excitons localised in the interfacial potential of narrow GaAs=Al 0:31 Ga 0:69 As quantum wells. These behave in many respects as quantum dot excitons, and give narrow emission lines that permit direct resolution of Zeeman splittings. Some dots show small zero-field splitting (< 100 meV), varying down to below the limit of resolution of our technique (% 25 meV). For these dots the excitonic g-factor depends on well-width, and also shows variation with the applied field B. The variation with B is related to the band mixing which is more prominent in these weakly-confined dots than in, for example, typical Stranski-Krastanow dots. The magnitude of the term linear in B can be calculated in a simplified model of the confined state, which gives a method of estimating the lateral extent of the confining potential. For particular transitions which are found at the extreme low-energy end of the emission from wells of 2 nm and 3 nm width, a different behaviour is found. These show much larger zero-field splitting of around 1 meV, and much smaller diamagnetic shift than that in the more usual dots with small zero-field splitting. The measured spin fine structure of these states is compared with that calculated from a spin Hamiltonian for a heavy-hole exciton, which gives a unique determination of the full three-dimensional g-factor for a single quantum dot.

From the artificial atom to the Kondo-Anderson model: Orientation-dependent magnetophotoluminescence of charged excitons in InAs quantum dots

“…g sz e and g z h are the s-electron and hole Landé factors along the dot axis, respectively, and c z /2 is the isotropic exchange splitting. 10,31 Away from Faraday geometry, the in-plane component of the magnetic field introduces some mixing between the X 0 bright and dark states. Accordingly, two additional emission lines are observed for fields larger than about 2 T [ Figure 5(b,c)].…”

Microstructural origins of localization in InGaN quantum wells

“…The possibility of slight (1 or 2 monolayer ) fluctuations in the QW's width has received far less attention. Such monolayer well-width fluctuations can localise carriers in GaAs-based QWs, with quantum dot-like optical behaviour being observed in such samples at low temperatures [38]. This is due to the reduction of the impact of quantum confinement on the electron and hole energy levels as the QW width increases.…”

Single-photon sources with optical fibre integration

“…Normally the fibre is glued on the top of the quantum dot wafer with an ultra-violet light curing optical adhesive [5,6,7]. To obtain single dot emission through a fibre with a mode field size around 5 µm in diameter, the dot density should be extremely low.…”

“…Therefore, new designs for stable single-photon sources are desirable. Attaching an optical fibre to a quantum dot wafer is one of the methods to avoid these problems [5,6,7].…”