Structural and electronic properties of the type I InAs/GaAs and type II GaSb/GaAs quantum dots

Informacje na temat projektu

Identyfikator umowy o grant: INTAS-94-1028

Projekt został zamknięty

Data rozpoczęcia 1 Sierpnia 1995

Data zakończenia 31 Lipca 1997

Finansowanie w ramach

• International Association for the promotion of cooperation with scientists from the independent states of the former Soviet Union (INTAS), 1993-

Koszt całkowity € 0,00

Wkład UE € 61 000,00

Koordynowany przez

Technische Universität Berlin
Germany

Exploitable results

Structural and electronic properties of type I InAs-GaAs and Type II GaSb/GaAs quantum dots

During the project duration time the five teams involved in this project achieved many important results. Quantum Dot lasers with exceptionally high performance were fabricated both by MBE and MOCVD and characterised. Ultra-high material gain was demonstrated. Ultralow threshold current density is realised (60 A/cm-² at 300K). First high power InGaAs-AlGaAs lasers based on vertically-coupled QDs operating at 1 W CW at RT were fabricated by MBE. First vertical cavity surface emitting lasers with low threshold current density lasers based on vertically coupled QDs ( 180 A/cm-², RT) in stripe geometry were fabricated. 2. Vertically coupled quantum dots were fabricated and their optical properties studied. Enhancement of exciton oscillator strength by stacking of dots was demonstrated. Magneto-optical properties of QDs were investigated. 3. Type-II GaSb-GaAs QDs were fabricated and their optical properties were studied. We demonstrated the tunability of type-II QD optical properties by change in the excitation density due to electric field between holes in the GaSb QD and electrons in the GaAs region. 4. Theoretical modelling of QD formation was performed. It is shown that for reasonable values of surface stress, formation of laterally ordered array of equisized and equishaped QDs can be energetically favorable. 5. Detailed calculations of strain distribution and piezoelectric effects for realistic pyramid-like InAs QDs with { 101 } side facets and successive numerical solution of the Schrödinger equation show that only one electron but several hole states exist in quantum dot of typical size (below 200 Å). Only 3/2, 3/2> hole states play a role, and only excited hole states due to quantization in z-direction 001 > (002>) have a non vanishing optical transition matrix element with the ground electron state. The predictions of the caculations including excitonic effects are in good agreement with the optical data.