Investigation of the optical properties, composition and local structure of InGaN

Rights statement
Awarding institution
  • University of Strathclyde
Date of award
  • 2002
Thesis identifier
  • T10446
Qualification Level
Qualification Name
Department, School or Faculty
  • his thesis presents work on the optical properties, composition and local structure of InGaN. Low temperature photoluminescence (PL) spectroscopy of InGaN epilayers was used to study linewidth, intensity and uniformity of the samples. Temperature dependence of the PL spectrum showed a decrease in the peak emission energy with increasing temperature for one epilayer sample and an 'S'- shape temperature dependence of peak emission energy for a second sample. Composition analysis of the epilayers using three different experimental techniques; Rutherford backscattering spectrometry (RBS), electron probe microanalysis (EPMA) and extended X-ray absorption fine structure (EXAFS), found that the indium nitride fraction varies linearly with the PL peak emission energy. Confocal microscopy of InGaN epilayer, quantum well (QW) and quantum box (QB) samples revealed that InGaN luminescence segregates into bright and dark spots, ~1 µm in diameter, and indicates that the origin of InGaN luminescence is of sub µm-scale. InGaN local structure parameters were derived from EXAFS measurements. Epilayer samples exhibited a single-phase InGaN alloy while a QB sample showed a two-phase mixture of components, one of which is nearly pure InN. Photoluminescence excitation (PLE) spectroscopy on MOCVD epilayers and MBE QWs and QBs showed that the bandgap energy varies linearly with detected emission energy for an individual sample. The PLE results from the MOCVD samples were consistent with data taken using optical absorption spectroscopy. Two different linear relationships between Stokes' shift and detected emission energy were obtained for the MOCVD and MBE samples. Analysis of the accumulated results suggests that InGaN luminescence may be related to the combined effects of exciton localisation in InN-rich QDs, formed as a result of phase segregation in InGaN, accompanied by strain-induced piezoelectric fields.
Advisor / supervisor
  • O'Donnell, Kevin
Resource Type