Abstract
Carrier tunnelling through GaAs barriers of different thicknesses is investigated in vertically InGaAs/GaAs quantum rings (QR’s). Shorter PL decay time of the ground state emission of high-energy component in the sample with thicker spacer (1.5 nm) is ascribed to both tunnelling effect between the two QR families and vertical coupling between layers in the stacks. We found that tunnelling time between QR’s followed the Wentzel-Kramers-Brillouin (WKB) approximation. The non resonant tunnelling rate between QR’s is found to be different by one order of magnitude from the rate in quantum dots (QD’s).
Highlights
Tunneling of carriers in semiconductor heterostructures has been intensively investigated because of its basic quantum mechanical aspect [1,2,3] and the importance for both physics and applied physic
In QD, the estimation of PL decay time down to 20 ps has been attributed to carrier transfer between different layers of QD stacks separated by GaAs spacer layer, from the smaller QDs in the seed layer to the larger quantum dots (QD’s) in the second layer [3]
We evaluated the tunnelling time between the two QR families (P1 to P2) from the observed decay times using the following equation:
Summary
Tunneling of carriers in semiconductor heterostructures has been intensively investigated because of its basic quantum mechanical aspect [1,2,3] and the importance for both physics and applied physic. In QD, the estimation of PL decay time down to 20 ps has been attributed to carrier transfer between different layers of QD stacks separated by GaAs spacer layer, from the smaller QDs in the seed layer to the larger QD’s in the second layer [3]. The tunnelling time is 130 ps for the vertically stacked In0.9Al0.1As with barrier thickness of 6 nm [2]. PL and TRPL for In(Ga)As/GaAs QRs in such stacked samples show the energy transfer processes between layers and allows the estimation of the non resonant carrier tunnelling time in vertically aligned triple QR’s structures. We present a detailed study of the carrier transfer between two QR families with different slight average size distribution, but separated by a thin GaAs spacer layer.
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