InAS Quantum Dots for Laser Applications and Pedogogical, Gender, and Multicultural Aspects in Engineering Education
Doctoral thesis, 2005
This thesis builds on new cross-disciplinary research between engineering and educational sciences. Recently, two other theses that combine research in physics and education (Åke Ingerman, 2002, and Tom Adawi, 2002) have been completed in Sweden. This thesis consolidates a trend that can benefit both disciplines. It is similar to the other theses in that it focuses on engineering education and investigates knowledge formation in a scientific subject. It differs in that the scientific study concerns a different area of physics. Its original contribution is that it focuses on the pedagogical, socio-cultural and gendered context in which learning in engineering education takes place and does so by means of a cross cultural, autobiographical case study and three action research projects. These projects deal with a pedagogy of e-learning (paper E), developing generic capabilities in online learning (papers C and E), learning in groups (papers B and G) and gender equity in physics (paper D). The thesis is divided into two parts. The study in engineering science (photonics) was successfully defended at the licentiate level and is reported in appended paper A and in published articles (papers H to M). The pedagogical study in engineering education is reported in the following chapters and in papers B to G.
The scientific engineering study concerns the development of InAs Quantum Dot (QD) structures on GaAs substrate for 1.3 μm laser applications and investigations of how structural and optical properties of InAs QDs depend on the growth conditions and the choice of pre-layer and cap materials. Growth conditions for the best luminance intensity and line width were found for substrate temperatures (500-520oC) and nominal InAs layer thickness (3.3-3.7 monolayers). It was found that the QD size was considerably reduced during initial GaAs capping, resulting in a blue-shift of the emission wavelength. The density of the QDs also reduces significantly during GaAs capping. Using an Al-containing cap layer the size reduction can be suppressed, and therefore a longer emission wavelength can be obtained. The density of QDs can also be increased. Furthermore, introducing a thin InAlAs cap layer resulted in 1.3 μm emission with a large energy separation between the ground and the first excited state transmission. A record transition energy separation of 108 meV was demonstrated.
InAs quantum dots
self-organised quantum dots
molecular beam epitaxy
quantum dot lasers