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Author: | Muraleedharan, Sony |
Title: | Processing of gallium nitride blue light emitting diode chips |
Publication type: | Master's thesis |
Publication year: | 2007 |
Pages: | vii + 55 s. + liitt. 8 Language: eng |
Department/School: | Sähkö- ja tietoliikennetekniikan osasto |
Main subject: | Optoelektroniikka (S-104) |
Supervisor: | Sopanen, Markku |
Instructor: | Törmä, Pekka |
OEVS: | Electronic archive copy is available via Aalto Thesis Database.
Instructions Reading digital theses in the closed network of the Aalto University Harald Herlin Learning CentreIn the closed network of Learning Centre you can read digital and digitized theses not available in the open network. The Learning Centre contact details and opening hours: https://learningcentre.aalto.fi/en/harald-herlin-learning-centre/ You can read theses on the Learning Centre customer computers, which are available on all floors.
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Location: | P1 Ark S80 | Archive |
Keywords: | light emitting diodes gallium nitride compound semiconductor ternary compouds photoluminescence lithography ICP-RIE etching e-beam evaporation lift-off electro-luminescence measurement |
Abstract (eng): | In this thesis, processing of gallium nitride based blue light emitting diodes (LEDs) from as-grown wafers into LED chips was studied. The LED wafers had been grown using a metal organic chemical vapour deposition (MOCVD) system. The aim of the work was to introduce process variations in the fabrication procedure in order to optimize the light intensity and voltage drop of the fabricated LEDs. The processing steps performed include multiple steps of ultra violet (UV) lithography, electron beam (e-beam) evaporation, inductively coupled plasma reactive ion etching (ICP-RIE) and lift-off. The facilities of Micro and Nanosciences Laboratory at TKK were used for successfully carrying out the fabrication process. After the fabrication, some of the LED chips were subjected to electro-luminescence (EL) measurements to investigate the effects of the process variations on the light output and voltage drop of the LEDs. During the etching of LED mesas tetrachlorosilane (SiCl4) was introduced. This step caused a favorable change in the light output of the fabricated LEDs. Another set of LEDs was fabricated with a platinum (Pt) current spreading layer (CSL) instead of the normal Ni/Au CSL. This gave a better light homogeneity for the fabricated LEDs. Also the chamber pressure and the sample biasing power during etching were varied. Optimal values for the parameter range studied were found. It will be worthwhile to continue in the future by trying out different flows of SiCl4 to see whether the light intensity of LEDs can still be improved. As the PtCSL gave a better light homogeneity, fabricating LEDs each with a varying thickness of the Pt CSL will be a good direction to take. |
ED: | 2008-03-13 |
INSSI record number: 35419
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