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Investigation on the role of indium in the removal of metallic gallium from soft and hard sputtered GaN (0001) surfaces
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
KTH, School of Information and Communication Technology (ICT), Material Physics, Material Physics, MF.
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2009 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 517, no 21, 6023-6026 p.Article in journal (Refereed) Published
Abstract [en]

Cleaning of GaN by argon sputtering and subsequent annealing introduces metallic gallium on the GaN surface. Once formed, this metallic gallium can be difficult to remove. it has a strong influence on the Fermi level position in the band gap and poses a problem for subsequent epitaxial growth on the surface. We present a method of removing metallic gallium from moderately damaged GaN surfaces by deposition of indium, and formation of an In-Ga alloy that can be desorbed by annealing at similar to 550 degrees C. After the In-Ga alloy has desorbed, photoemission spectra show that the Ga3d bulk component becomes narrower indicating a smoother and more homogeneous surface. This is also reflected in a sharper low energy electron diffraction pattern. On heavily damaged GaN surfaces, caused by hard sputtering, larger amount of metallic gallium forms after annealing at 600 degrees C. This gallium readily alloys with deposited indium, but the alloy does not desorb until a temperature of 840 degrees C is reached and even then, traces of both indium and metallic gallium could be found on the surface.

Place, publisher, year, edition, pages
2009. Vol. 517, no 21, 6023-6026 p.
Keyword [en]
Gallium nitride, Surfactant, Cleaning, Indium, Argon sputtering, Surface defects, Photoemission spectroscopy, stoichiometric gan(0001)-1 x-1, core-level photoemission, molecular-beam epitaxy, electron accumulation, ion-bombardment, n-type, deposition, nitride
URN: urn:nbn:se:kth:diva-18636DOI: 10.1016/j.tsf.2009.05.023ISI: 000268438200013ScopusID: 2-s2.0-67449127658OAI: diva2:336683
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-12-10Bibliographically approved
In thesis
1. Surface studies on α–sapphire for potential use in GaN epitaxial growth
Open this publication in new window or tab >>Surface studies on α–sapphire for potential use in GaN epitaxial growth
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This Licentiate thesis summarizes the work carried out by the author the years 2004 to 2008 at the University of Iceland and the Royal Institute of Technology (KTH) in Sweden. The aim of the project was to investigate the structure of sapphire (alpha-Al2O3) surfaces, both for pure scientific reasons and also for potential use as substrate for GaN-growth by molecular beam epitaxy.

More generally the thesis describes some surface science methods used for investigating the substrates; the general physical back ground, the experi- mental implementation and what information they can give. The described techniques are used for surface analysis on sapphire substrates which have been treated variously in order to optimize them for use as templates for epi- taxial growth of GaN or related III-V compounds.

The thesis is based on three published papers.

The first paper focuses on the formation a thin AlN layer on sapphire, which may act as a buffer layer for potential epitaxial growth of GaN or any related III-V materials. Two types of sapphire substrates (reconstructed and non- reconstructed) were exposed to ammonia resulting in the formation of AlN on the surface. The efficiency of the AlN formation (nitridation efficiency) for the two surfaces was then compared as a function of substrate temperature through photoelectron spectroscopy and low electron energy diffraction. The reconstructed surface showed a much higher nitridation efficiency than the non-reconstructed surface.

In the second paper, the affect of different annealing processes on the sapphire morphology, and thus its capability to act as a template for GaN growth, was studied. Atomic force microscopy, X-ray diffraction analysis together with ellipsometry measurements showed that annealing in H2 ambient and subse- quent annealing at 1300 °C in O2 for 11 hours resulted in high quality and atomically flat sapphire surface suitable for III-V epitaxial growth.

The third paper describes the effect of argon sputtering on cleaning GaN surfaces and the possibility of using indium as surfactant for establishing a clean and stoichiometric GaN surface, after such sputtering. Soft sputtering, followed by deposition of 2 ML of indium and subsequent annealing at around 500 °C resulted in a well ordered and clean GaN surface while hard sputtering introduced defects and incorporated both metallic gallium and indium in the surface.

Place, publisher, year, edition, pages
KTH, 2009. xi, 49 p.
Trita-ICT/MAP, 2009:3
National Category
Condensed Matter Physics
urn:nbn:se:kth:diva-10669 (URN)978-91-7415-286-9 (ISBN)
2009-06-05, Sal/Hall C1, KTH-Electrum, Isafjordsgatan 26, Kista, 10:15 (English)
Available from: 2009-06-22 Created: 2009-06-13 Last updated: 2010-11-03Bibliographically approved

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