Experimental and theoretical study of polarization-dependent optical transitions in InAs quantum dots at telecommunication-wavelengths (1300-1500 nm)

Abstract

The design of some optical devices such as semiconductor optical amplifiers for telecommunication applications requires polarization-insensitive optical emission at the long wavelengths (1300-1550 nm). Self-assembled InAs/GaAs quantum dots (QDs) typically exhibit ground state optical emission at wavelengths shorter than 1300 nm with highly polarization-sensitive characteristics, although this can be modified by using low growth rates, the incorporation of strainreducing capping layers or growth of closely-stacked QD layers. Exploiting the strain interactions between closely stacked QD layers also allows greater freedom in the choice of growth conditions for the upper layers, so that both a significant extension in their emission wavelength and an improved polarization response can be achieved due to modification of the QD size, strain and composition. In this paper we investigate the polarization behavior of single and stacked QD layers using room temperature sub-lasing-threshold electroluminescence and photovoltage measurements as well as atomistic modeling with the NEMO 3-D simulator. A reduction is observed in the ratio of the transverse electric (TE) to transverse magnetic (TM) optical mode response for a GaAs-capped QD stack compared to a single QD layer, but when the second layer of the two-layer stack is InGaAs-capped an increase in the TE/TM ratio is observed, in contrast to recent reports for single QD layers.

In-plane polarization anisotropy of ground state optical intensity in InAs/GaAs quantum dots

“…5,23 Among these techniques, the exploitation of strain interactions between the quantum dot layers in multi-layer QD stacks have shown great potential to generate polarization-insensitive optical transitions at telecommunication wavelengths. 2,4,22,24,53 B. Aspect ratio of QDs increases above 0.3…”

“…Thus, a directional degree of polarization (DOP) should be measured (or calculated) to fully characterize the polarization response of quantum dot stacks. Previous theoretical and experimental studies have considered only a single value of DOP: either [110] The electronic structure of single and stacked InAs quantum dots (QDs) has been extensively studied in the last couple of decades for the design of optical devices [1][2][3][4][5][6][7][8] and devices suited to quantum information processing. [9][10][11][12] Recent efforts are focused to achieve isotropic polarization response of ground state optical intensity (GSOI) at telecommunication wavelengths (1300-1500 nm).…”

“…Several methods have been explored to reduce the value of DOP. These methods include (1) strain engineering by over-growing the InAs QDs with InGaAs quantum wells, also known as the strain reducing capping layers, 3 (2) inclusion of dilute impurities such as nitrogen "N," 19 antimony "Sb," 20 and phosphorous "P," 21 etc., (3) exploiting the strain interaction between the QDs in multi-layer QD stacks, 2,4,22 and (4) growing large stacks of QDs in the form of columnar QDs. 5,23 Among these techniques, the exploitation of strain interactions between the quantum dot layers in multi-layer QD stacks have shown great potential to generate polarization-insensitive optical transitions at telecommunication wavelengths.…”

“…[9][10][11][12] Recent efforts are focused to achieve isotropic polarization response of ground state optical intensity (GSOI) at telecommunication wavelengths (1300-1500 nm). 2,[4][5][6][7] The polarization response of QD samples is characterized in terms of degree of polarization:…”

Наногетероструктуры С Улучшенными Параметрами Для Быстродействующих И Высокоэффективных Плазмон-Поляритонных Светодиодов Шоттки

“…Для объяснения этого эффекта можно предложить следующую модель. Расчеты [12] упругих напряжений и зонной структуры гетеросистемы с двумя слоями квантовых точек показывают, что слой InAs испытывает напряжения сжатия, а слой GaAs -растягивающие напряжения, в результате чего подзона легких дырок в GaAs поднимается по энергии выше подзоны тяжелых дырок GaAs, но все же остается ниже энергии подзоны тяжелых дырок в КТ InAs. Сильное электрическое поле увеличивает интеграл перекрытия волновых функций электронов в КТ InAs и легких дырок в GaAs.…”