TY - JOUR
T1 - Alloyed β-(Al xGa1- x)2O3bulk Czochralski single β-(Al0.1Ga0.9)2O3and polycrystals β-(Al0.33Ga0.66)2O3, β-(Al0.5Ga0.5)2O3), and property trends
AU - Jesenovec, Jani
AU - Dutton, Benjamin
AU - Stone-Weiss, Nicholas
AU - Chmielewski, Adrian
AU - Saleh, Muad
AU - Peterson, Carl
AU - Alem, Nasim
AU - Krishnamoorthy, Sriram
AU - Mccloy, John S.
N1 - Funding Information:
This material is based upon work supported by the Air Force Office of Scientific Research under Award No. FA9550-21-1-0078 monitored by Dr. Ali Sayir. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the United States Air Force. The authors thank David Bollinger for tireless discussion and advice concerning Rietveld refinement as well as Brooke Downing for technical support. The authors also thank Billy Schmuck at the WSU for some assistance with XRD measurements. Finally, they also thank Arkka Bhattacharyya for discussions concerning AGO thin films and devices.
Publisher Copyright:
© 2022 Author(s).
PY - 2022/4/21
Y1 - 2022/4/21
N2 - In this work, bulk Czochralski-grown single crystals of 10 mol. % Al2O3 alloyed β-Ga2O3 - monoclinic 10% AGO or β-(Al0.1Ga0.9)2O3 - are obtained, which show +0.20 eV increase in the bandgap compared with unintentionally doped β-Ga2O3. Further, growths of 33% AGO - β-(Al0.33Ga0.67)2O3 - and 50% AGO - β-(Al0.5Ga0.5)2O3 or β-AlGaO3 - produce polycrystalline single-phase monoclinic material (β-AGO). All three compositions are investigated by x-ray diffraction, Raman spectroscopy, optical absorption, and 27Al nuclear magnetic resonance (NMR). By investigating single phase β-AGO over a large range of Al2O3 concentrations (10-50 mol. %), broad trends in the lattice parameter, vibrational modes, optical bandgap, and crystallographic site preference are determined. All lattice parameters show a linear trend with Al incorporation. According to NMR, aluminum incorporates on both crystallographic sites of β-Ga2O3, with a slight preference for the octahedral (GaII) site, which becomes more disordered with increasing Al. Single crystals of 10% AGO were also characterized by x-ray rocking curve, transmission electron microscopy, purity (glow discharge mass spectroscopy and x-ray fluorescence), optical transmission (200 nm-20 μm wavelengths), and resistivity. These measurements suggest that electrical compensation by impurity acceptor doping is not the likely explanation for high resistivity, but rather the shift of a hydrogen level from a shallow donor to a deep acceptor due to Al alloying. Bulk crystals of β-(Al0.1Ga0.9)2O3 have the potential to be ultra-wide bandgap substrates for thin film growth, with a lattice parameter that may even allow higher Al concentration β-Ga2O3 single crystal thin films to be grown.
AB - In this work, bulk Czochralski-grown single crystals of 10 mol. % Al2O3 alloyed β-Ga2O3 - monoclinic 10% AGO or β-(Al0.1Ga0.9)2O3 - are obtained, which show +0.20 eV increase in the bandgap compared with unintentionally doped β-Ga2O3. Further, growths of 33% AGO - β-(Al0.33Ga0.67)2O3 - and 50% AGO - β-(Al0.5Ga0.5)2O3 or β-AlGaO3 - produce polycrystalline single-phase monoclinic material (β-AGO). All three compositions are investigated by x-ray diffraction, Raman spectroscopy, optical absorption, and 27Al nuclear magnetic resonance (NMR). By investigating single phase β-AGO over a large range of Al2O3 concentrations (10-50 mol. %), broad trends in the lattice parameter, vibrational modes, optical bandgap, and crystallographic site preference are determined. All lattice parameters show a linear trend with Al incorporation. According to NMR, aluminum incorporates on both crystallographic sites of β-Ga2O3, with a slight preference for the octahedral (GaII) site, which becomes more disordered with increasing Al. Single crystals of 10% AGO were also characterized by x-ray rocking curve, transmission electron microscopy, purity (glow discharge mass spectroscopy and x-ray fluorescence), optical transmission (200 nm-20 μm wavelengths), and resistivity. These measurements suggest that electrical compensation by impurity acceptor doping is not the likely explanation for high resistivity, but rather the shift of a hydrogen level from a shallow donor to a deep acceptor due to Al alloying. Bulk crystals of β-(Al0.1Ga0.9)2O3 have the potential to be ultra-wide bandgap substrates for thin film growth, with a lattice parameter that may even allow higher Al concentration β-Ga2O3 single crystal thin films to be grown.
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U2 - 10.1063/5.0073502
DO - 10.1063/5.0073502
M3 - Article
AN - SCOPUS:85128927829
SN - 0021-8979
VL - 131
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 15
M1 - 155702
ER -