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Progress in Sputter Growth of β ‐Ga 2 O 3 by Applying Pulsed‐Mode Operation
Author(s) -
Schurig Philipp,
Michel Fabian,
Beyer Andreas,
Volz Kerstin,
Becker Martin,
Polity Angelika,
Klar Peter J.
Publication year - 2020
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201901009
Subject(s) - sputtering , materials science , analytical chemistry (journal) , thin film , sapphire , annealing (glass) , sputter deposition , pulsed dc , high power impulse magnetron sputtering , argon , duty cycle , optoelectronics , optics , nanotechnology , atomic physics , chemistry , metallurgy , voltage , laser , quantum mechanics , physics , chromatography
β ‐Ga 2 O 3 thin films are deposited by pulsed radio‐frequency (RF) magnetron sputtering on c‐sapphire substrates, using a stoichiometric Ga 2 O 3 target and a constant gas flux of an argon–oxygen mixture. Pulsed sputtering offers a way to overcome the restrictions of conventional sputtering. The parameters RF power and pulse duty cycle (PDC) are varied systematically to optimize the synthesis of Ga 2 O 3 thin films. Subsequently, the resulting as‐deposited (AD) Ga 2 O 3 layers are analyzed in terms of structural and optical properties and the results are compared with those on the samples treated by postdeposition rapid thermal annealing. Based on this analysis, the process parameters are evaluated in terms of β ‐Ga 2 O 3 formation. Postdeposition temperature treatments are found to yield a better crystal quality. However, a strong interdiffusion with the Al 2 O 3 substrate is observed. The optical bandgap of the sputtered thin films is found to be quite independent of the RF sputtering power but to depend strongly on the PDC used, whereas the layer thickness rather strongly increases with both of those growth parameters. These evolutions are assigned to changes in the energy and ionic species of the plasma. Traces of GaO x ‐related phases in addition to β ‐Ga 2 O 3 are found in the interphase between the growing thin films and the underlying substrate.