Gain characteristics of InAs/GaAs self-organized quantum-dot lasers

Harris, L.; Ashmore, A.; Mowbray, D. J.; Skolnick, M. S.; Hopkinson, M.; Hill, G.; Clark, Joseph

doi:10.1063/1.125372

Cited by 19 publications

(13 citation statements)

References 11 publications

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“…Self-assembled semiconductor quantum dots (QDs) grown by Stranski-Krastanov mode have emerged as an attractive subject in terms of fundamental physics and potential device application [1,2]. It has been theoretically predicted that the device performances would be greatly enhanced by adopting QDs as an active medium [2,3].…”

Section: Introductionmentioning

confidence: 99%

Formation of self-assembled InAs quantum dots on InAl(Ga)As/InP and effects of a thin GaAs layer

Lee

Hong

Han

et al. 2003

Journal of Crystal Growth

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Section: Introductionmentioning

confidence: 99%

Formation of self-assembled InAs quantum dots on InAl(Ga)As/InP and effects of a thin GaAs layer

Lee

Hong

Han

et al. 2003

Journal of Crystal Growth

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“…This can even prohibit lasing from the ground state in some QD structures. [3][4][5] Previous theoretical studies 6,7 suggested that the low gain arises because the built-in piezoelectric field leads to the ground state hole wave function being elongated, with the matrix element then reduced due to lower overlap between the electron and hole wave functions. We show here that this is not the only reason for low optical matrix element.…”

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confidence: 99%

Optical matrix element in InAs∕GaAs quantum dots: Dependence on quantum dot parameters

Andreev

O’Reilly²

2005

Applied Physics Letters

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We present a theoretical analysis of the optical matrix element between the electron and hole ground states in InAs/ GaAs quantum dots ͑QDs͒ modeled with a truncated pyramidal shape. We use an eight-band k·p Hamiltonian to calculate the QD electronic structure, including strain and piezoelectric effects. The ground state optical matrix element is very sensitive to variations in both the QD size and shape. For all shapes, the matrix element initially increases with increasing dot height, as the electron and hole wave functions become more localized in k space. Depending on the QD aspect ratio and on the degree of pyramidal truncation, the matrix element then reaches a maximum for some dot shapes at intermediate size beyond which it decreases abruptly in larger dots, where piezoelectric effects lead to a marked reduction in electron-hole overlap. © 2005 American Institute of Physics. ͓DOI: 10.1063/1.2130378͔ Semiconductor quantum dots ͑QDs͒ have been widely studied because of their unique fundamental properties and also because they are considered to be promising candidates for a new generation of semiconductor laser.1 One of the main advantages initially proposed for QDs was the atomiclike ͑zero-dimensional͒ density of states, which should provide a relatively large optical gain at a reduced carrier density.2 In real QD structures the gain is, however, significantly reduced due both to inhomogeneous broadening of the atomic-like density of states and also because of a reduced optical matrix element. This can even prohibit lasing from the ground state in some QD structures.3-5 Previous theoretical studies 6,7 suggested that the low gain arises because the built-in piezoelectric field leads to the ground state hole wave function being elongated, with the matrix element then reduced due to lower overlap between the electron and hole wave functions. We show here that this is not the only reason for low optical matrix element. The QDs in Refs. 6 and 7 were assumed to be pyramidal with a base to height aspect ratio of 2. In real structures the typical QD shape is markedly different, strongly influencing the electron and hole wave functions, 8 and thereby modifying the optical matrix element. Previous theoretical studies of InAs/ GaAs QDs either do not contain calculations of the optical matrix element 8,9 or consider only one specific QD shape. 10The aim of this letter is to identify the factors determining the ground state optical matrix element in QDs, and its dependence on QD shape and size. In a bulk semiconductor the optical matrix element decreases for transitions away from the Brillouin zone center, and also depends on the wave vector direction with respect to the light polarization. This fundamental property of semiconductors, as well as the piezoelectric effect, causes the matrix element in QDs to be very sensitive to variations in the QD geometrical parameters, leading to a lower optical matrix element in QDs compared to the maximum "ideal" band edge value of a bulk semiconductor.To calculate the electronic s...

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“…In Refs. [7,14,15] and [10] values of about 12, 2.5, 11 and 8 cm --1 per sheet, respectively, were reported. The electroluminescence (EL) spectra are taken from the first section (100 mm), for the lowest and the highest injection current density as indicated.…”

mentioning

confidence: 89%