Photoluminescence studies of the electronic structure in some III-V quantum structures

Sammanfattning: Semiconductor compound materials from groups III and V in the periodic table have attracted much interest during recent years, due to promising properties for optoelectronic devices such as lasers and light emitting diodes. Most of these devices are fabricated from quantum well (QW) structures. This thesis is based on optical studies on quantum wells and modulation doped heterostructures in some important III-V material systems: InGaAs/lnP, InGaN/GaN and GaN/AlGaN. The experimental investigations involve photoluminescence (PL), PL excitation (PLE) and time-resolved PL spectroscopy. Simple theoretical models have been used in some cases to compare with and identify experimental data.In the InGaAs/lnP material system, the dependence of the electronic structure on both In content (and thereby built-in strain) and well width has been studied by means of Fourier transform (FT) PL and FTPLE for a set of QW samples. The reduced effective masses for the same set of samples have been determined by applying external magnetic fields and fitting the experimental data to Landau levels. Similar experiments have also been performed on a set of modulation doped heterostructures, where a self-consistent calculation enabled peak identification as well as a suggestion for a probable potential profile.Electronic structure and optical transitions have been studied in a modulation doped GaN/AlGaN QW and compared to calculations based on a simple model. Also, the recombination processes involved in the PL from InGaN/GaN multi QW samples have been investigated. The In content and the growth condition for the barriers were varied. In a set of Si doped samples with different doping concentrations, the screening of the strain induced piezoelectric field was studied.

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