Publication detail

Local optical phenomena in InAs/GaAs heterostructures with doped quantum dots and artificial molecules (Seoul, Korea)

TOMÁNEK, P., GRMELA, L.

Original Title

Local optical phenomena in InAs/GaAs heterostructures with doped quantum dots and artificial molecules (Seoul, Korea)

Czech Title

Lokální optické jevy v InAs/GaAs heterostrukturách s dotovanými kvantovými tečkami a umělými molekulami (Seoul, Korea)

English Title

Local optical phenomena in InAs/GaAs heterostructures with doped quantum dots and artificial molecules (Seoul, Korea)

Type

abstract

Language

en

Original Abstract

In a bulk 3-D semiconductor material, the interaction between atoms in the crystal lattice extends the energy levels of free electron and hole charge carriers into a continuous spectrum. Transition due to the stimulated recombination of electron-hole pairs between conduction and valence bands results in light emission over a broad distribution of wavelengths. The deposition of thin layers makes possible the freedom of motion of charge carriers to be localized by confinement on a nanometer-scale in one, two or three dimensions between heteroboundaries with wider bandgap surrounding materials. This restricts carriers to 2-D quantum wells, 1-D quantum wires or 0-D quantum dots. Such size quantization in the confined directions concentrates available energy levels for injected carriers into the increased density of states near the band edges. In the case of the QDs, localized carriers confined in all three dimensions have their density of states concentrated into fully quantizated, discrete and hence mode widely separated energy levels. Optical transitions between them are therefore restricted to emission at fewer wavelengths with atomic-like spectrally narrowed linewidths. These wavelengths are not determined solely by the fixed bandgap energy of the active region material, but also by the QDs energy levels, which depend on QD size and band offsets at the heteroboundary. This property allow tune over a wider range. Therefore an investigation of internal optical transitions of charge carriers in the quantum dots (QDs) is of a vital importance for the design of new optoelectronic devices as sources and detectors operating in near and mid infrared domains. The photoinduced internal absorption in undoped InAs/GaAs quantum dots and an absorption in undoped n-type QDs has been studied, but the data proceeded from internal intrazonal light absorption in the n-type QDs as well as an analysis of absorption in n- and p-types are still missing. Among different other characteristics, these data might be interesting especially for the evaluation of optical losses, due to the light absorption by holes in the laser with internal transition of electrons in the QDs. This paper brings an experimental and theoretical study of internal absorption in InAs/GaAs quantum dots. The comparison of the near- and far-field induced photoabsorption will be also provided.

Czech abstract

3D polovodiče jsou charakterizovány rozšiřování energetických hladin do spojitého spektra v důsledku interakce mezi atomy v krystalové mřížce. Přechod způsobený stimulovanou rekombinací páru elektron-díra mezi vodivým a valenčním pásem se projeví emisí světla v širokém pásmu vlnovoých délek. Depozice tenkých vrstev umožní, že volný pohyb nosičů náboje bude lokalizován na nanometrické rozměry v jedno-, dvou- a tří-rozměrném prostoru rozhraní s materiálem s širším zakázaným pásem, čímž vzniknou 2-D kvantové jámy, 1-D drátky a 0-D tečky. Tato kvantifikace velikosti koncentruje vhodné energetické hladiny pro injektované nosiče do zvýšené hustoty stavů v blízkosti hran pásů. V případě kvantových teček mají lokalizované nosiče koncentrovánu svou hustotu stavů do plně kvantovaných, diskrétních energetických hladin. Optické přechody mezi nimi jsou tedy omezeny na záření pouze v několika vlnových délkách, čímž vytvářejí prakticky čárové spektrum podobné vyzařování atomů. Tyto vlnové délky nejsou vyjádřeny pouze fixovanými energiemi zakázaného pásu z materiálu aktivní oblasti, ale též hladinami energie kvantových teček, které závisejí na velikosti teček a zakázaném pásu na heterorozhraní. Tato vlastnost umožní ladění v širokém oboru vlnových délek. Proto zkoumání vnitřních optických přechodů nosičů nábojů v kvantových tečkách je životně důležité pro návrh nových optoelektronických zařízení jako jsou zdroje a detektory pracující v blízké a střední IČ oblasti spektra. Je studována fotoindukovaná vnitřní absorpce v nedotovaných InAs/GaAs kvantových tečkách a absorpce v nedotovaných n- kvantových tečkách, ale data z vnitří mezizónové absorpce světla od n- a p-typů stále ještě nejsou k dispozici. Mezi jiným mohou být tato data zajímavá zejména pro hodnocení optických ztrát způsobených absorpcí na děrách v laserech s vnitřním přechodem elektronů v kvantové tečce.Článek přináší experimentální a teoretické zkoumání vnitřní absorpce v InAs/GaAs kvantových tečkách. Jsou porovnána měření indukované fotoabsorpce ve vzdáleném a blízkém poli.

English abstract

In a bulk 3-D semiconductor material, the interaction between atoms in the crystal lattice extends the energy levels of free electron and hole charge carriers into a continuous spectrum. Transition due to the stimulated recombination of electron-hole pairs between conduction and valence bands results in light emission over a broad distribution of wavelengths. The deposition of thin layers makes possible the freedom of motion of charge carriers to be localized by confinement on a nanometer-scale in one, two or three dimensions between heteroboundaries with wider bandgap surrounding materials. This restricts carriers to 2-D quantum wells, 1-D quantum wires or 0-D quantum dots. Such size quantization in the confined directions concentrates available energy levels for injected carriers into the increased density of states near the band edges. In the case of the QDs, localized carriers confined in all three dimensions have their density of states concentrated into fully quantizated, discrete and hence mode widely separated energy levels. Optical transitions between them are therefore restricted to emission at fewer wavelengths with atomic-like spectrally narrowed linewidths. These wavelengths are not determined solely by the fixed bandgap energy of the active region material, but also by the QDs energy levels, which depend on QD size and band offsets at the heteroboundary. This property allow tune over a wider range. Therefore an investigation of internal optical transitions of charge carriers in the quantum dots (QDs) is of a vital importance for the design of new optoelectronic devices as sources and detectors operating in near and mid infrared domains. The photoinduced internal absorption in undoped InAs/GaAs quantum dots and an absorption in undoped n-type QDs has been studied, but the data proceeded from internal intrazonal light absorption in the n-type QDs as well as an analysis of absorption in n- and p-types are still missing. Among different other characteristics, these data might be interesting especially for the evaluation of optical losses, due to the light absorption by holes in the laser with internal transition of electrons in the QDs. This paper brings an experimental and theoretical study of internal absorption in InAs/GaAs quantum dots. The comparison of the near- and far-field induced photoabsorption will be also provided.

Keywords

InAs/GaAs heterostructure, quantum dots, artificial molecules, near-field, local optical phenomena,

Released

05.09.2004

Publisher

Seoul National University

Location

Seoul, Korea

Pages from

248

Pages to

248

Pages count

1

BibTex


@misc{BUT59968,
  author="Pavel {Tománek} and Lubomír {Grmela}",
  title="Local optical phenomena in InAs/GaAs heterostructures with doped quantum dots and artificial molecules (Seoul, Korea)",
  annote="In a bulk 3-D semiconductor material, the interaction between atoms in the crystal lattice extends the energy levels of free electron and hole charge carriers into a continuous spectrum. Transition due to the stimulated recombination of electron-hole pairs between conduction and valence bands results in light emission over a broad distribution of wavelengths.
The deposition of thin layers makes possible the freedom of motion of charge carriers to be localized by confinement on a nanometer-scale in one, two or three dimensions between heteroboundaries with wider bandgap surrounding materials. This restricts carriers to 2-D quantum wells, 1-D quantum wires or 0-D quantum dots. Such size quantization in the confined directions concentrates available energy levels for injected carriers into the increased density of states near the band edges. In the case of the QDs, localized carriers confined in all three dimensions have their density of states concentrated into fully quantizated, discrete and hence mode widely separated energy levels. Optical transitions between them are therefore restricted to emission at fewer wavelengths with atomic-like spectrally narrowed linewidths. These wavelengths are not determined solely by the fixed bandgap energy of the active region material, but also by the QDs energy levels, which depend on QD size and band offsets at the heteroboundary. 
 This property allow tune over a wider range. Therefore an investigation of internal optical transitions of charge carriers in the quantum dots (QDs) is of a vital importance for the design of new optoelectronic devices as sources and detectors operating in near and mid infrared domains.  The photoinduced internal absorption in undoped InAs/GaAs quantum dots and an absorption in undoped n-type QDs has been studied, but the data proceeded from internal intrazonal light absorption in the n-type QDs as well as an analysis of absorption in n- and p-types are still missing.
Among different other characteristics, these data might be interesting especially for the evaluation of optical losses, due to the light absorption by holes in the laser with internal transition of electrons in the QDs.

This paper brings an experimental and theoretical study of internal absorption in InAs/GaAs quantum dots.  The comparison of the near- and far-field induced photoabsorption will be also provided. 


",
  address="Seoul National University",
  booktitle="The 8th International Conference on Near-field Nano Optics and Related Techniques (NFO-8)",
  chapter="59968",
  institution="Seoul National University",
  year="2004",
  month="september",
  pages="248",
  publisher="Seoul National University",
  type="abstract"
}