硅酸盐学报

雾化学气相外延法异质外延Ga₂O₃薄膜的生长特性

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谢佳慧 ¹ , 穆文祥 ¹ , 李竹程 ¹ , 李光清 ¹ , 李阳 ¹ , 贾志泰 ¹^,² , 陶绪堂 ¹

硅酸盐学报 | 国家自然科学基金重点项目中期成果专题—研究论文 2024,52(2): 373-380

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硅酸盐学报 |国家自然科学基金重点项目中期成果专题—研究论文 2024 , 52 (2) : 373 -380

雾化学气相外延法异质外延Ga₂O₃薄膜的生长特性

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谢佳慧¹, 穆文祥¹, 李竹程¹, 李光清¹, 李阳¹, 贾志泰¹^,², 陶绪堂¹

作者信息

^1．山东大学，晶体材料国家重点实验室，新一代半导体材料研究院，晶体材料研究院，济南 250100

^2．山东省工业技术研究院，济南 250100

通讯作者:

穆文祥（1989—），男，博士，副教授；

李阳（1990—），女，博士，副研究员；

陶绪堂（1962—），男，博士，教授。

作者简介:

谢佳慧（1999—），女，硕士研究生。

Growth Characterization of Heterogeneous Epitaxial Gallium Oxide Films by Mist Chemical Vapor Deposition

Jiahui XIE¹, Wenxiang MU¹, Zhucheng LI¹, Guangqing LI¹, Yang LI¹, Zhitai JIA¹^,², Xutang TAO¹

Affiliations

^1.State Key Laboratory of Crystal Materials, Institute of Novel Semiconductors, Institute of Crystal Materials, Shandong University, Jinan 250100, China

^2.Shandong Research Institute of Industrial Technology, Jinan 250100, China

Corresponding Author:

MU Wenxiang (1989-), male, Ph.D., Associate Professor. E-mail: mwx@sdu.edu.cn

LI Yang (1990-), female, Ph.D., Associate Professor. yangli@sdu.edu.cn

TAO Xutang (1962-), male, Ph.D., Professor. txt@sdu.edu.cn

XIE Jiahui (1999-), female, Master Candidate. E-mail: 202114051@mail.sdu.edu.cn

出版时间: 2024-02-20 doi: 10.14062/j.issn.0454-5648.20230451

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摘要

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氧化镓各晶相的应用广泛，亚稳相只能通过外延的手段获得。选择合适的生长方法和提高异质外延水平仍是学术界一直探讨的问题。采用雾化学气相沉积（Mist-CVD）法在蓝宝石衬底上异质外延生长了氧化镓薄膜，通过优化工艺条件实现了物相调控，系统研究了外延膜的结晶质量、组分和表面形貌，以及生长速率变化规律。同时，探究了Mist-CVD生长系统中，Ga₂O₃外延膜的晶体成核及晶相控制机理。在原有α-Ga₂O₃生长工艺的基础上，制备了α/ε混相薄膜、ε-Ga₂O₃纯相薄膜，呈三维岛状生长模式。在ε-Ga₂O₃纯相薄膜的基础上，随着氧气流量的增加，结晶质量先稳定后下降，生长速率先增加后降低，最高达到3μm/h。通过退火，获得了β-Ga₂O₃纯相薄膜，表面粗糙度由10.80 nm降低至5.42 nm。在利用Mist-CVD法进行不同晶相外延调控及其生长机理研究方面具有一定借鉴意义。

关键词

氧化镓 / 异质外延 / 雾化学气相沉积法 / 蓝宝石衬底

Abstract

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Introduction

Gallium oxide crystal phase is widely used, and the metastable phase can be only obtained by means of epitaxy. Selecting suitable growth methods and improving the heteroepitaxy level are still the problems that the academic circles have been discussing. The mist chemical vapour deposition (Mist-CVD) method does not require a vacuum system, which is safe, economical, simple and controllable, demonstrating a potential application for metastable phase growth of gallium oxide. The level of heterogeneous epitaxy of various crystalline phases of gallium oxide still needs to be further improved. For instance, there is still a problem of mixing phases during the growth process, which leads to a difficulty of regulating the crystalline phases. In terms of the nucleation mechanism, there is a lack of process-specific research and explanatory notes. In this paper, the most suitable growth intervals of Ga₂O₃ crystalline phases on sapphire substrates were explored in a vertical mist chemical vapour deposition epitaxy furnace. The relationships among Ga₂O₃ crystal phase modulation, crystalline quality, growth rate and growth process parameters, as well as the optimisation of surface morphology by annealing were investigated respectively. The nucleation mechanism of the films and the precursor droplet motion law of Mist-CVD were analyzed, and the experimental results were discussed.

Methods

Heterogeneous epitaxial Ga₂O₃ films were prepared by the Mist-CVD method in a vertical mist chemical vapour deposition epitaxy furnace with a 2-inch commercial sapphire substrate. Gallium acetylacetonate (Ga(acac)₃) aqueous solution was used as a precursor for Ga and O at 0.05 mol/L, and 1.5% HCl was used as a co-solvent. High-purity Ar (99.999%) was used as a carrier gas with Ar flow rate of 2 250 mL/min and growth pressure of 101.325 kPa, respectively, and O₂ was used as a dilution gas. The growth parameters were adjusted in the growth temperature range from 600 ℃ to 750 ℃ and O₂ flow rate from 225 mL/min to 600 mL/min for 1 h.

A model D8-ADVANCE X-ray diffractometer (XRD) was used to determine the crystal structure. The elemental composition and content of the epitaxial layer surfaces were determined using a model ESCALAB-250 X-ray photoelectron spectrometer (XPS). In addition, the cross-sectional image and thickness of the Ga₂O₃ epitaxial layer were characterized by a model S-4800 scanning electron microscope (SEM). The AFM images and root-mean-square (RMS) surface roughness of Ga₂O₃ epitaxial layers were analyzed by a model ICON-type atomic force microscope (AFM). A LAMBDA-950 UV-Vis spectrophotometer (UV-Vis) was used to characterize the transmittance of the samples and calculate the forbidden band width.

Results and discussion

Based on the XRD analysis on the crystal structure of the epitaxial films of gallium oxide at 600-750 ℃, there exist α and ε mixed phases at 600-700 ℃, and the film diffraction peaks are weak with no obvious selective orientation. This is due to the higher lattice matching of the α phase to the c-plane sapphire substrate, which is more easily induced to grow on the sapphire substrate at low temperatures and stabilised under lattice mismatch strain. The ε-pure phase is grown at 750 ℃ with a selective orientation. The crystalline phase of gallium oxide at higher temperatures is not explored, and pure phase films of β-Ga₂O₃ are expected to be obtained at higher growth temperatures due to the limitations of the current epitaxial furnace equipment with a maximum set temperature of 750 ℃.

ε-Ga₂O₃ pure phase is generated at different oxygen flow rates. However, the half-height width of the diffraction peaks of the films appears at a lower level of 0.141° and 0.150° for oxygen flow rates at 225-250 mL/min. When the oxygen flow rate exceeds 400 mL/min, the half-height widths of the samples become larger, i.e., 0.178°, 0.162° and 0.162°, respectively, and the crystalline quality of the films decreases, but the overall crystalline quality of ε-Ga₂O₃ is better. Based on the analysis on the cross-section of the film thickness by SEM, the growth rate of the film firstly increases and then decreases with the increase of the oxygen flow rate, reaching a growth rate of 3 μm/h at 250 mL/min and 400 mL/min. A higher growth rate can be obtained at 250-400 mL/min.

For the ε-Ga₂O₃ samples grown at 750 ℃, the surface of the ε-Ga₂O₃ sample shows a cluster with coarser particles and a cloudy morphological features, and its surface roughness is 10.8 nm. From the 3D stereogram, the surface morphology shows multiple bulge-like or hill-like bumps, and the height of the surface bumps is between 50 nm and 100 nm, and its overall height is larger than the grain size of the film, indicating that the epitaxial film grows in accordance with the three-dimensional island-like growth mode. The β-Ga₂O₃ sample after annealing at 900 ℃ is similarly characterized by AFM. The surface roughness of the thin film of β-Ga₂O₃ samples decreases as RMS=5.42 nm, and the grain size becomes larger, ranging from 50 nm to 80 nm. At high temperatures, the height of the surface bumps is between 5 nm and 30 nm, which is smaller than the grain size, showing that the film densities increase at high temperatures.

Conclusions

Pure phase films of ε-Ga₂O₃ were obtained at 750 ℃ in a three-dimensional island growth pattern with a high surface roughness of 10.8 nm at low temperatures. The growth rate of the film of ε-Ga₂O₃ at an oxygen flow rate of 225 mL/min was 1 μm/h with a half-height width of 0.141°. The growth rate of the film increased to 3 μm/h with increasing the oxygen flow rate, and the film was still in the pure phase of ε-Ga₂O₃. However, the crystalline quality of ε-Ga₂O₃ was not improved, while rather deteriorated due to the high oxygen flow rate. β-Ga₂O₃ pure-phase thin films were obtained after annealing at 900 ℃, and the surface morphology was further optimized with a reduced roughness of only 5.42 nm. The pure crystalline phases of Ga₂O₃ with a considerable thickness could be prepared by a low-cost mist chemical vapor deposition method in a Mist-CVD equipment.

Key words

gallium oxide / heterogeneous epitaxy / mist chemical vapour deposition / sapphire substrate

引用本文

谢佳慧, 穆文祥, 李竹程, 李光清, 李阳, 贾志泰, 陶绪堂. 雾化学气相外延法异质外延Ga₂O₃薄膜的生长特性. 硅酸盐学报, 2024 , 52 (2) : 373 -380 . DOI: 10.14062/j.issn.0454-5648.20230451

Jiahui XIE, Wenxiang MU, Zhucheng LI, Guangqing LI, Yang LI, Zhitai JIA, Xutang TAO. Growth Characterization of Heterogeneous Epitaxial Gallium Oxide Films by Mist Chemical Vapor Deposition[J]. Journal of the Chinese Ceramic Society, 2024 , 52 (2) : 373 -380 . DOI: 10.14062/j.issn.0454-5648.20230451

基金

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国家自然科学基金(51932004; 52002219)

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2024年第52卷第2期

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文章信息

doi: 10.14062/j.issn.0454-5648.20230451

接收时间：2023-06-29
首发时间：2026-10-22
出版时间：2024-02-20

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收稿日期：2023-06-29
修回日期：2023-08-24

基金

国家自然科学基金(51932004; 52002219)

作者信息

^1．山东大学，晶体材料国家重点实验室，新一代半导体材料研究院，晶体材料研究院，济南 250100

^2．山东省工业技术研究院，济南 250100

通讯作者:

穆文祥（1989—），男，博士，副教授；

李阳（1990—），女，博士，副研究员；

陶绪堂（1962—），男，博士，教授。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20230451

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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