Effect of Oxygen Partial Pressure on β -Ga2O3 Single Crystals Grown by Optical Floating Zone Method

doi:10.16553/j.cnki.issn1000-985x.2025.0264

Abstract

Abstract: Gallium oxide （Ga₂O₃） is a representative fourth-generation semiconductor with unique physical properties and the advantage of readily available large-area single crystals. These characteristics make Ga₂O₃ highly attractive for deep-ultraviolet photodetection and high-efficiency power electronic applications. Oxygen vacancies are among the most common intrinsic point defects in oxide semiconductors and play a crucial role in determining the material quality and device performance of Ga₂O₃. Therefore， effective control of oxygen vacancies in Ga₂O₃ single crystals is of significant practical importance. In this work，β-Ga₂O₃ single crystals were grown by optical floating zone method， which enables crucible-free growth and high material purity. A precisely controlled Ar/O₂ mixed atmosphere was employed to systematically investigate the effect of oxygen partial pressure on oxygen vacancy defect concentration inβ-Ga₂O₃ single crystals. With increasing oxygen content in the growth atmosphere， the optical transmittance ofβ-Ga₂O₃ single crystals is markedly enhanced， and the lattice ordering is significantly improved. Meanwhile， the defect-related photoluminescence emission is strongly suppressed. X-ray photoelectron spectroscopy analyses of the O 1s anion and Ga 3d cation states consistently demonstrate that the oxygen vancancy defect concentration decreases with increasing oxygen partial pressure. These results indicate that oxygen partial pressure is an effective parameter for regulating oxygen vacancy defect concentration inβ-Ga₂O₃ single crystals. This study provides practical guidance for the growth of high-quality oxide semiconductor single crystals.

Key words: gallium oxide; optical floating zone method; oxygen vacancy; oxygen partial pressure; single crystal; X-ray photoelectron spectroscopy

CLC Number:

O782

LI Xinpeng, LI Shan, FENG Ganrong, QI Song, JI Xueqiang, TANG Weihua, XIA Changtai. Effect of Oxygen Partial Pressure on β -Ga₂O₃ Single Crystals Grown by Optical Floating Zone Method[J]. Journal of Synthetic Crystals, 2026, 55(5): 697-705.

Figures/Tables 12

Fig.1 Schematic diagram of crystal growth by OFZ method （a）， photographs ofβ-Ga2O3 single crystals grown under different oxygen partial pressures （b）， and their XRD patterns （c）

Table 1 Raman peak fitting of UIDβ -Ga2O3 and β -Ga2O3 under different oxygen partial pressures

Raman mode	Peak/cm^-1
Raman mode	Reference^［16］	OFZ-5% O₂	OFZ-10% O₂	OFZ-15% O₂	OFZ-20% O₂
$A g (1)$	111.0	115.7	115.9	115.6	115.9
$B g (2)$	144.8	146.4	146.3	146.4	146.5
$A g (2)$	169.9	171.4	171.4	171.4	171.4
$A g (3)$	200.2	201.9	201.9	201.9	201.9
$A g (4)$	320.0	322.0	322.5	321.5	322.5
$A g (5)$	346.6	348.9	348.5	348.6	348.6
$A g (6)$	416.2	418.4	418.3	418.4	418.4
$A g (7)$	474.9	477.3	477.4	477.5	477.4
$A g (8)$	630.0	632.3	632.2	632.3	632.0
$A g (9)$	658.3	659.3	660.1	660.5	660.3
$A g (10)$	766.7	768.7	768.8	768.7	768.7

Table 1 Raman peak fitting of UIDβ -Ga2O3 and β -Ga2O3 under different oxygen partial pressures

Raman mode	Peak/cm^-1
Raman mode	Reference^［16］	OFZ-5% O₂	OFZ-10% O₂	OFZ-15% O₂	OFZ-20% O₂
$A g (1)$	111.0	115.7	115.9	115.6	115.9
$B g (2)$	144.8	146.4	146.3	146.4	146.5
$A g (2)$	169.9	171.4	171.4	171.4	171.4
$A g (3)$	200.2	201.9	201.9	201.9	201.9
$A g (4)$	320.0	322.0	322.5	321.5	322.5
$A g (5)$	346.6	348.9	348.5	348.6	348.6
$A g (6)$	416.2	418.4	418.3	418.4	418.4
$A g (7)$	474.9	477.3	477.4	477.5	477.4
$A g (8)$	630.0	632.3	632.2	632.3	632.0
$A g (9)$	658.3	659.3	660.1	660.5	660.3
$A g (10)$	766.7	768.7	768.8	768.7	768.7

Fig.2 Raman spectra ofβ-Ga2O3 under different oxygen partial pressures

Fig.3 UV-Vis-NIR transmission spectra （a） and band gap （b） ofβ-Ga2O3 under different oxygen partial pressures

Fig.4 Emission spectra ofβ-Ga2O3 single crystals under different oxygen partial pressures

Table 2 Fitted emission peak parameters of β -Ga2O3 under different oxygen partial pressures

Sample	Area		Position
Sample	UV	BL	UV	BL
OFZ-5% O₂	65.1	49.5	382.4	452.2
OFZ-10% O₂	68.9	41.8	377.0	450.9
OFZ-15% O₂	68.7	38.0	375.2	449.9
OFZ-20% O₂	71.0	30.1	373.3	448.3

Fig.5 Full spectra scanning ofβ-Ga2O3 under different oxygen partial pressures

Fig.6 O 1s fine scanning spectra and peak fitting under different oxygen partial pressures

Table 3 O 1s peak fitting and oxygen vacancy defect concentration under different oxygen partial pressures

Sample	Concentration/%
Sample	O（I）	O（II）	O（III）	V_O
OFZ-5% O₂	63.7	28.9	7.4	31.2
OFZ-10% O₂	64.4	25.2	10.4	28.1
OFZ-15% O₂	65.8	23.4	10.8	26.2
OFZ-20% O₂	69.4	20.0	10.6	22.4

Fig.7 Fine scanning spectra and peak fitting of Ga 3d-O 2s under different oxygen partial pressures

Table 4 Ga 3d-O 2s peak fitting and oxygen vacancy defect concentration under different oxygen partial pressures

Sample	Ga³⁺ ratio/%	Ga⁺ ratio/%	Concentration of V_O/%
OFZ-5% O₂	70.9	29.1	19.4
OFZ-10% O₂	75.1	24.9	16.6
OFZ-15% O₂	80.5	19.5	13.0
OFZ-20% O₂	86.2	13.8	9.2

Table 5 Effective area and O/Ga atomic ratio of Ga 3d-O 2s and O 1s peaks in β -Ga2O3 single crystals under different oxygen partial pressures

Sample	Effective area		O/Ga atomic ratio
Sample	O 1s	Ga 3d	O/Ga atomic ratio
OFZ-5% O₂	3 571.1	3 506.5	1.02
OFZ-10% O₂	3 656.6	3 518.4	1.04
OFZ-15% O₂	3 356.5	3 050.9	1.10
OFZ-20% O₂	3 239.9	2 502.7	1.29

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Effect of Oxygen Partial Pressure on β -Ga₂O₃ Single Crystals Grown by Optical Floating Zone Method

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