Giant Stark effect in the emission of single semiconductor quantum dots

Abstract

We study the quantum-confined Stark effect in single InAs/GaAs quantum dots embedded within a AlGaAs/GaAs/AlGaAs quantum well. By significantly increasing the barrier height we can observe emission from a dot at electric fields of 500 kVcm -1 , leading to Stark shifts of up to 25 meV. Our results suggest this technique may enable future applications that require selfassembled dots with transitions at the same energy.Single InGaAs/GaAs quantum dots (QDs) provide a fascinating test-bed for investigating quantum effects in the solid state. A large number of papers have studied the properties of these QDs under vertical electric field. For devices that rely upon controlled charging of single dots 1 or tuning a dot relative to a coherent laser 2,3 it is sufficient to shift the transitions by a few times the linewidth.However, the relatively low energy offset between quantized transitions and the surrounding GaAs cladding (1.52 eV band-gap at 4K) means fields of only a few tens of kVcm -1 can be applied before electrons tunnel out. When the tunneling rate is comparable to the radiative recombination rate the emission efficiency falls and the transition broadens in a well-understood manner 4,5 . At larger fields some transitions can be identified by using a narrow-linewidth laser to create carriers, which then tunnel out as photocurrent 4,5,6,7 , but these devices are not useful for photon emission.The tunneling of carriers can be quantified using the well-known formula for the tunneling rate from a 1D confined state through a triangular barrier 8, 12.

Scalable qubit architecture based on holes in quantum dot molecules

“…40 Tuning over 10 meV is an order of magnitude improvement over the typical Stark shift tuning (of order 1 meV) achieved for single InAs QDs 14 and comparable to the giant Stark shift that can be achieved for single QDs confined between AlGaAs barriers. 41 In our QDM design the AlGaAs layer that blocks injection of carriers from the n-type GaAs can be moved arbitrarily far away from the QDs. As a result, our QDM design is likely to be more compatible with the fabrication of photonic crystal cavities than single QDs that achieve a giant Stark shift by placing AlGaAs layers in close proximity to the QDs.…”

Voltage control of electron-nuclear spin correlation time in a single quantum dot

“…The design includes thick AlGaAs barriers to allow for wide range electric field tuning while avoiding the tunnelling out of photo-generated carriers. Such devices have previously been used to tune the energy of different exciton complexes [16], to observe the coherent coupling between neutral exciton states [12] and to control the electron-and hole g-factors [17]. Distributed Bragg reflectors placed outside the tunnelling barriers create an optical cavity (weak coupling), enhancing the light collection efficiency around the emission wavelengths of the quantum dots (∼940 nm).…”

Independent indistinguishable quantum light sources on a reconfigurable photonic integrated circuit

“…We observe transitions from predominantly neutral and positively charged states below À1 V and predominantly negatively charged states above. 29 We select two adjacent diodes, D5 and D6, to demonstrate that photons from separated QDs can be rendered indistinguishable. Both were simultaneously optically excited through the waveguide circuit and QD photons collected through a single channel, as shown in Fig.…”