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Title: Comparison of the growth kinetics of In{sub 2}O{sub 3} and Ga{sub 2}O{sub 3} and their suboxide desorption during plasma-assisted molecular beam epitaxy

Abstract

We present a comprehensive study of the In{sub 2}O{sub 3} growth kinetics during plasma-assisted molecular beam epitaxy and compare it to that of the related oxide Ga{sub 2}O{sub 3} [P. Vogt and O. Bierwagen, Appl. Phys. Lett. 108, 072101 (2016)]. The growth rate and desorbing fluxes were measured during growth in-situ by a laser reflectometry set-up and line-of-sight quadrupole mass spectrometer, respectively. We extracted the In incorporation as a function of the provided In flux, different growth temperatures T{sub G}, and In-to-O flux ratios r. The data are discussed in terms of the competing formation of In{sub 2}O{sub 3} and desorption of the suboxide In{sub 2}O and O. The same three growth regimes as in the case of Ga{sub 2}O{sub 3} can be distinguished: (i) In-transport limited, O-rich (ii) In{sub 2}O-desorption limited, O-rich, and (iii) O-transport limited, In-rich. In regime (iii), In droplets are formed on the growth surface at low T{sub G}. The growth kinetics follows qualitatively that of Ga{sub 2}O{sub 3} in agreement with their common oxide and suboxide stoichiometry. The quantitative differences are mainly rationalized by the difference in In{sub 2}O and Ga{sub 2}O desorption rates and vapor pressures. For the In{sub 2}O, Ga{sub 2}O, and Omore » desorption, we extracted the activation energies and frequency factors by means of Arrhenius-plots.« less

Authors:
;  [1]
  1. Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5–7, D-10117 Berlin (Germany)
Publication Date:
OSTI Identifier:
22594347
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 109; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ACTIVATION ENERGY; COMPARATIVE EVALUATIONS; DESORPTION; DROPLETS; GALLIUM OXIDES; INDIUM OXIDES; KINETICS; LASERS; MASS SPECTROMETERS; MOLECULAR BEAM EPITAXY; MOLECULAR BEAMS; PLASMA; STOICHIOMETRY; SURFACES; TEMPERATURE DEPENDENCE; VAPOR PRESSURE; VAPORS

Citation Formats

Vogt, Patrick, E-mail: vogt@pdi-berlin.de, and Bierwagen, Oliver, E-mail: bierwagen@pdi-berlin.de. Comparison of the growth kinetics of In{sub 2}O{sub 3} and Ga{sub 2}O{sub 3} and their suboxide desorption during plasma-assisted molecular beam epitaxy. United States: N. p., 2016. Web. doi:10.1063/1.4960633.
Vogt, Patrick, E-mail: vogt@pdi-berlin.de, & Bierwagen, Oliver, E-mail: bierwagen@pdi-berlin.de. Comparison of the growth kinetics of In{sub 2}O{sub 3} and Ga{sub 2}O{sub 3} and their suboxide desorption during plasma-assisted molecular beam epitaxy. United States. doi:10.1063/1.4960633.
Vogt, Patrick, E-mail: vogt@pdi-berlin.de, and Bierwagen, Oliver, E-mail: bierwagen@pdi-berlin.de. Mon . "Comparison of the growth kinetics of In{sub 2}O{sub 3} and Ga{sub 2}O{sub 3} and their suboxide desorption during plasma-assisted molecular beam epitaxy". United States. doi:10.1063/1.4960633.
@article{osti_22594347,
title = {Comparison of the growth kinetics of In{sub 2}O{sub 3} and Ga{sub 2}O{sub 3} and their suboxide desorption during plasma-assisted molecular beam epitaxy},
author = {Vogt, Patrick, E-mail: vogt@pdi-berlin.de and Bierwagen, Oliver, E-mail: bierwagen@pdi-berlin.de},
abstractNote = {We present a comprehensive study of the In{sub 2}O{sub 3} growth kinetics during plasma-assisted molecular beam epitaxy and compare it to that of the related oxide Ga{sub 2}O{sub 3} [P. Vogt and O. Bierwagen, Appl. Phys. Lett. 108, 072101 (2016)]. The growth rate and desorbing fluxes were measured during growth in-situ by a laser reflectometry set-up and line-of-sight quadrupole mass spectrometer, respectively. We extracted the In incorporation as a function of the provided In flux, different growth temperatures T{sub G}, and In-to-O flux ratios r. The data are discussed in terms of the competing formation of In{sub 2}O{sub 3} and desorption of the suboxide In{sub 2}O and O. The same three growth regimes as in the case of Ga{sub 2}O{sub 3} can be distinguished: (i) In-transport limited, O-rich (ii) In{sub 2}O-desorption limited, O-rich, and (iii) O-transport limited, In-rich. In regime (iii), In droplets are formed on the growth surface at low T{sub G}. The growth kinetics follows qualitatively that of Ga{sub 2}O{sub 3} in agreement with their common oxide and suboxide stoichiometry. The quantitative differences are mainly rationalized by the difference in In{sub 2}O and Ga{sub 2}O desorption rates and vapor pressures. For the In{sub 2}O, Ga{sub 2}O, and O desorption, we extracted the activation energies and frequency factors by means of Arrhenius-plots.},
doi = {10.1063/1.4960633},
journal = {Applied Physics Letters},
number = 6,
volume = 109,
place = {United States},
year = {Mon Aug 08 00:00:00 EDT 2016},
month = {Mon Aug 08 00:00:00 EDT 2016}
}
  • By systematically changing growth parameters, the growth of β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3}/Ga{sub 2}O{sub 3} (010) heterostructures by plasma-assisted molecular beam epitaxy was optimized. Through variation of the Al flux under O-rich conditions at 600 °C, β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (010) layers spanning ∼10% to ∼18% Al{sub 2}O{sub 3} were grown directly on β-Ga{sub 2}O{sub 3} (010) substrates. Nominal β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (010) compositions were determined through Al:Ga flux ratios. With x = ∼0.18, the β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (020) layer peak in a high-resolution x-ray diffraction (HRXRD) ω-2θ scan was barely discernible, and Pendellösung fringes were not visible.more » This indicated that the phase stability limit of Al{sub 2}O{sub 3} in β-Ga{sub 2}O{sub 3} (010) at 600 °C was less than ∼18%. The substrate temperature was then varied for a series of β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3} (010) layers, and the smoothest layer was grown at 650 °C. The phase stability limit of Al{sub 2}O{sub 3} in β-Ga{sub 2}O{sub 3} (010) appeared to increase with growth temperature, as the β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (020) layer peak with x = ∼0.18 was easily distinguishable by HRXRD in a sample grown at 650 °C. Cross-sectional transmission electron microscopy (TEM) indicated that β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3} (010) layers (14.4% Al{sub 2}O{sub 3} by energy dispersive x-ray spectroscopy) grown at 650 °C were homogeneous. β-(Al{sub ∼0.20}Ga{sub ∼0.80}){sub 2}O{sub 3} (010) layers, however, displayed a phase transition. TEM images of a β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3}/Ga{sub 2}O{sub 3} (010) superlattice grown at 650 °C showed abrupt layer interfaces and high alloy homogeneity.« less
  • The authors demonstrate the heteroepitaxial and homoepitaxial growth of single crystalline {beta}-Ga{sub 2}O{sub 3} by plasma-assisted molecular beam epitaxy. Phase-pure (201) and (100) {beta}-Ga{sub 2}O{sub 3} thin films were grown on c-plane sapphire and (100) {beta}-Ga{sub 2}O{sub 3} substrates, respectively. Based on the homoepitaxial results, detailed information is reported on the dependence between the {beta}-Ga{sub 2}O{sub 3} film quality and various growth parameters. At an optimized growth temperature of 700 deg. C, a growth relationship between growth rates and increasing gallium fluxes was established at a fixed oxygen pressure. A three-dimensional columnar growth with a relatively high growth rate wasmore » measured at a low gallium flux while a terrace surface morphology with a reduced growth rate was observed as the gallium flux increased. The gallium flux played an important role on both surface morphology and growth rate. We associated the decreasing growth rate with increasing gallium flux with the formation of gallium suboxides monitored by quadrupole mass spectrometry. The formation and desorption of volatile gallium suboxides limited the resulting growth rate of {beta}-Ga{sub 2}O{sub 3} growth.« less
  • Thin films of In{sub 2}O{sub 3} have been grown on Y-stabilized ZrO{sub 2}(100) by oxygen plasma assisted molecular beam epitaxy with a substrate temperature of 650 deg. C. Ordered epitaxial growth was confirmed by high resolution transmission electron microscopy. The position of the valence band onset in the x-ray photoemission spectra of the epitaxial films is found to be inconsistent with the widely quoted value of 3.75 eV for the fundamental bandgap of In{sub 2}O{sub 3} and suggests a revised value of 2.67 eV.
  • Epitaxial growth of {beta}-Ga{sub 2}O{sub 3} thin films by the rf-plasma-assisted molecular-beam epitaxy technique is demonstrated. Growth on (1 0 0) {beta}-Ga{sub 2}O{sub 3} substrates leads to very smooth epilayers, while (2 0 1) and (1 0 0) oriented {beta}-Ga{sub 2}O{sub 3} films are obtained on (0 0 1) sapphire and (1 0 0) MgO substrates, respectively. Internal transmittance, refractive index and direct bandgaps are determined.
  • High quality gallium doped ZnO (Ga:ZnO) thin films were grown on c-Al{sub 2}O{sub 3}(1000) by plasma-assisted molecular beam epitaxy, and Ga concentration N{sub Ga} was controlled in the range of 1x10{sup 18}-2.5x10{sup 20}/cm{sup 3} by adjusting/changing the Ga cell temperature. From the low-temperature photoluminescence at 10 K, the donor bound exciton I{sub 8} related to Ga impurity was clearly observed and confirmed by comparing the calculated activation energy of 16.8 meV of the emission peak intensity with the known localization energy, 16.1 meV. Observed asymmetric broadening with a long tail on the lower energy side in the photoluminescence (PL) emissionmore » line shape could be fitted by the Stark effect and the compensation ratio was approximately 14-17% at N{sub Ga}{>=}1x10{sup 20}/cm{sup 3}. The measured broadening of photoluminescence PL emission is in good agreement with the total thermal broadening and potential fluctuations caused by random distribution of impurity at N{sub Ga} lower than the Mott critical density.« less