Details

Autor(en) / Beteiligte

• Huang, Eddie Yu-yan

Titel

Infra-Red Cathodoluminescence in Gallium Phosphide

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

1984

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• This project was primarily aimed at the study of cathodoluminesce (cl) spectra from the semiconductor Gallium Phosphide (GaP), using a scanning electron microscope (SEM) with an efficient CL collection and transfer system developed in previous work. Particular emphasis was placed on CL in the infra-red region, arising from radiative recombination at deep levels. The high resolution of the SEM was utilised in the comparison of spectra at and away from dislocations, with a view to understanding the influence of dislocations on the distribution of various recombination centres.Although the main aim was to perform infra-red CL experiments, it was found in the initial investigations that the band-edge luminescence, in particular that due to nitrogen iso-electronic centres, though well- known, still afforded -much interesting study. The results obtained suggested an aggregation of the nitrogen centre to dislocations to form a Cottrell atmosphere of impurities.In the very near infra-red region, a radiative recombination centre was observed, also reported by other authors. Using computer calculations to isolate this peak from the long wavelength tail of band-edge luminescence, a comparison of the concentration of this centre in various samples (LEC, VPE, LPE, with different doping levels), at and away from dislocations, was performed. Clear evidence of the aggregation of this centre to dislocations was observed in LEC and VPE crystals. Some samples which were plastically deformed using a 4-point bending technique were also studied, and no aggregation of this centre to dislocations introduced by plastic deformation was observed.In the further infra-red region, where photomultipliers gave way to solid state photodetectors, more efficient means of spectral measurements had to be employed, namely multiplex spectroscopy using a Michelson interferometer, A commercially available interferometer was adapted for this purpose, using Fabry-Perot interference from a He-Ne laser beam to control the path difference. Detailed testing of the system was performed using standard light sources and GaP with visible band-edge luminescence, to highlight the necessary precautions when using this technique. Then CL spectra from different samples of GaP in the infra-red region were recorded, employing Fourier transform in a digital computer for the recovery of spectra from interferograms, Two chromium-doped GaP layers gave distinct CL emission in the infra-red, similar to those observed by other workers. The centre in question, however, did not appear to aggregate to dislocations.Some other interesting results, although not directly related to the main aim of the project, are also reported in this thesis, as they may form the basis for further research work.