E-Locus - Institutional Repository of the University of Crete

Home Search

Results - Details

Search command : Author="Ηλιόπουλος" And Author="Γεώργιος"

Current Record: 35 of 75

[Add to Basket]

Identifier

000407250

Title

Characterization and growth of InGaN thin films by the sputtering method

Alternative Title

Χαρακτηρισμός κι ανάπτυξη λεπτών υμενίων με τη μέθοδο sputtering

Author

Γεωργάκης, Σπυρίδων Α.

Thesis advisor

Ηλιόπουλος, Ελευθέριος

Reviewer

Γεωργακίλας, Αλέξανδρος
Κυριακίδης, Γεώργιος

Abstract

In recent years, III-nitride semiconductor materials have become promising candidates for use in electronic and photovoltaic devices due to their wide direct bandgap that cover most of the solar spectrum (0.7-3.4 eV) [1]. In particular, solar cells based on group III nitrides have attracted much attention since InGaN has high light absorption coefficients. In this thesis, we study the fundamentals of deposition III-nitride thin films by radiofrequency (rf) reactive sputtering. The aim of this thesis is to investigate the growth of gallium nitride and indium gallium nitride films by RF sputtering that could be used in effective and inexpensive photovoltaic devices. It is imperative to point out that it is the first attempt to deposit III-nitride materials by RF sputtering in the labs of Microelectronics of FORTH/IESL. It was shown that no probable condensation and pre-cleaning of GaN powder target led to dominated oxynitride and oxide phases in grown thin films. However, we achieved to have a good control on the growth process, as a result, we could initiate growing GaN and InGaN films minimizing the oxygen incorporation in as-deposited samples. Hence, the optical properties of the films were studied by spectroscopic ellipsometry (SE) and the measured data were analyzed by taking into account the effects of surface roughness based on an effective medium approximation model. X-ray diffraction (XRD), Energy-dispersive X-ray (EDX) and Hall measurements were used to characterize the structural and electrical properties of films. The most crystalline GaN films were grown in a pure nitrogen atmosphere, low pressure and high target RF power. The optical bandgap of the optimum GaN films was determined to be approximately 3.4eV. As far as it concerns InGaN films, they were grown having optical bandgaps from 2.91 eV to 2.15 eV. The bandgap was tuning with the RF power and the number of indium pellets onto the target. After alloying with In, the XRD analysis revealed the amorphous phase of InGaN films. A resistivity as low as 0.14 Ω*cm with an electron concentration 3.38*10¹⁹ cm^-3 and mobility value of 1.55 cm²/Vs was obtained in In_0.3Ga_0.7N. Last but not least, it was attempted to deposit p-type GaN and InGaN films with Mg pellets that were placing onto the target. Hall effect measurements showed that when the Mg dopant content in In_0.24Ga_0.76N increased to 11.5 metallic at. % the as-sputtered film transformed into p-type conduction. This project was co-funded by the European Union (European Social Fund (ESF)) and the Greek national funds through the Operational Program ‘’Education and Lifelong Learning’’ of the National Strategic Reference Framework (NSRF)-Research Funding Program:THALES.

Language

English

Subject

Gallium nitride

Indium gallium nitride alloys

Mg-doping

RF sputtering

Issue date

2017-03-17

Collection

School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses

Type of Work--Post-graduate theses