Effect of strain on low-loss electron energy loss spectra of group III-nitrides
2011 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, no 24, 245301- p.Article in journal (Refereed) Published
Low-loss EELS was used to acquire information about the strain state in group III-nitrides. Experimental and theoretical simulation results show that the bulk plasmon peak position varies near linearly with unit cell volume variations due to strain. A unit cell volume change of 1% results in a bulk plasmon peak shift of 0.159 eV, 0.168 eV, and 0.079 eV for AlN, GaN, and InN, respectively, according to simulations. The AlN peak shift was experimentally corroborated with a peak shift of 0.156 eV, where the applied strain caused a 1% volume change. It is also found that while the bulk plasmon energy can be used as a measure of the composition in a III-nitride alloy for relaxed structures, the presence of strain significantly affects such a measurement. The strain has a lower impact on the peak shift for Al(1-x)InxN (3% compositional error per 1 % volume change) and In(1-x)GaxN alloys compared to significant variations for Al(1-x)GaxN (16% compositional error for 1% volume change). Hence low-loss studies off III-nitrides, particularly for confined structures, must be undertaken with care and understanding.
Place, publisher, year, edition, pages
American Physical Society , 2011. Vol. 84, no 24, 245301- p.
IdentifiersURN: urn:nbn:se:liu:diva-67981DOI: 10.1103/PhysRevB.84.245301ISI: 000297767800004OAI: oai:DiVA.org:liu-67981DiVA: diva2:414770