MOVPE Growth of InAlGaN Layers and Quantum structures for UV applications

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Helsinki University of Technology | Master's thesis
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Date

2007

Department

Sähkö- ja tietoliikennetekniikan osasto

Major/Subject

Optoelektroniikka

Mcode

S-104

Degree programme

Language

en

Pages

69

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Abstract

In this work aluminum gallium nitride (A1GaN) and indium aluminum gallium nitride (InAlGaN) films were grown by metalorganic vapor phase epitaxy (MOVPE) on sapphire-based GaN templates. After optimizing growth conditions for these layers, InGaN/InAlGaN multiple quantum well structures (MQW) were grown. The research was performed at Micro and Nanosciences Laboratory of Helsinki University of Technology. The effect of various growth parameters on the crystal quality and the optical properties of the films and MQW structures was studied. The surface morphology and etch pit density of the films were investigated with atomic force microscopy. The composition and thickness were analyzed by X-ray measurements and the optical properties were investigated with photoluminescence (PL) measurements. The effect of temperature, V/III ratio, and trimethyl aluminum/trimethyl gallium (TMAI/TMGa) ratio on the composition and the thickness of A1GaN layers was studied. An Al content of 23% in the A1GaN layers has been achieved at a temperature of 850°C. High V/III ratio dropped the Al content in the AGaN layers. An Al content of 38 % was achieved with a high TMAI/TMGa ratio by keeping the TMAI flow constant. With increasing TMAI/TMGa ratio the Al content increased linearly. Introducing TMI during the AJGaN growth linearly increased the In content in the grown layer. Good quality InA1GaN layers with an In content of 5.3 % and an Al content of 23 % were achieved at 850°C Improved surface morphology and PL emission were achieved for the quantum well structures with the InAIGaN barriers as compared to the A1GaN barriers. The In composition of 3.2 % in the barrier showed the best PL results. A strong dependence of the PL peak wavelength was found on the In flow during the cap layer growth. It was also found that thinner quantum wells blue shifted the PL peak wavelength

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Supervisor

Sopanen, Markku

Thesis advisor

Suihkonen, Sami

Keywords

gallium nitride, MOVPE, aluminum gallium nitride, indium gallium nitride, indium aluminum gallium nitride, ternary, quaternary, quantum wells, AFM, XRD, photoluminescence

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https://urn.fi/URN:NBN:fi:aalto-2020120553650

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[dipl] Teknillinen korkeakoulu / TKK