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Authors Hilfiker, M. ; Kilic, U. ; Mock, A. ; Darakchieva, V. ; Knight, S. ; Korlacki, R. ; Mauze, A. ; Zhang, Y. ; Speck, J. ; Schubert, M.
Title Dielectric function tensor (1.5 eV to 9.0 eV), anisotropy, and band to band transitions of monoclinic -(AlxGa1-x)(2)O-3 (x 0.21) films
Date 02.07.2019
Number 56850
Abstract A set of monoclinic ß-(AlxGa1–x)2O3 films coherently grown by plasma-assisted molecular beam epitaxy onto (010)-oriented ß-Ga2O3 substrates for compositions x·=·0.21 is investigated by generalized spectroscopic ellipsometry at room temperature in the spectral range of 1.5·eV–9.0·eV. We present the composition dependence of the excitonic and band to band transition energy parameters using a previously described eigendielectric summation approach for ß-Ga2O3 from the study by Mock et al. All energies shift to a shorter wavelength with the increasing Al content in accordance with the much larger fundamental band to band transition energies of Al2O3 regardless of crystal symmetry. The observed increase in the lowest band to band transition energy is in excellent agreement with recent theoretical predictions. The most important observation is that charge confinement in heterostructures will strongly depend on the growth condition due to the strongly anisotropic properties of the band to band transitions.<br />This work was supported in part by the National Science Foundation under Award No. DMR 1808715, the Air Force Office of Scientific Research under Award No. FA9550-18-1-0360, the Nebraska Materials Research Science and Engineering Center under Award No. DMR 1420645, the Swedish Energy Agency under Award No. P45396-1, the Swedish Research Council VR Award No. 2016-00889, the Swedish Foundation for Strategic Research Grant Nos. FL12-0181, RIF14-055, EM16-0024, and the Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University, Faculty Grant SFO Mat LiU No. 2009-00971. M.S. acknowledges the University of Nebraska Foundation and the J. A. Woollam Foundation for financial support. J.S.S, A.M., and Y.Z. acknowledge funding from AFOSR through programs FA9550-18-1-0059 and FA9550-18-1-0479, and DTRA through program HDTRA 11710034.
Publisher Applied Physics Letters
Wikidata
Citation Applied Physics Letters 114 (2019) 231901
DOI https://doi.org/10.1063/1.5097780
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