图形化与非图形化薄膜衬底上Na助熔剂法生长GaN晶体的研究

doi:10.16553/j.cnki.issn1000-985x.2025.0218

摘要/Abstract

摘要： 本研究采用Na助熔剂液相外延生长法，开展了不同温度下图形化（PS）与非图形化（NPS）薄膜衬底上GaN晶体的外延生长研究。结合COMSOL数值模拟，计算并分析了不同温度条件下Ga-Na熔体中的氮浓度分布及GaN过饱和度变化规律，从实验与数值模拟两方面系统研究了PS和NPS上GaN晶体外延生长行为的差异。研究结果表明，在PS上，仅在840和850 ℃下成功实现了接种与外延生长，所得晶体表面呈现规则的六方锥阵列形貌，断面中上部存在未完全填充间隙。随温度从840 ℃升至850 ℃，熔体中氮浓度升高，过饱和度降低，六方锥小面趋于光滑，整体厚度由约570 μm增至约810 μm；当温度进一步升至860 ℃时，熔体中过饱和度进一步降低，点籽晶完全溶解，无外延生长发生。与之相比，在NPS上，840~860 ℃均可实现稳定外延生长。随温度升高，熔体中过饱和度逐渐降低，晶体表面形貌由低温下的山脊状结构逐渐转变为平坦胞状结构，断面表现为横向连续且致密。晶体厚度随温度变化呈先增后减趋势，于850 ℃达到最大值约1 450 μm。此外，PS上所得GaN晶体的厚度显著小于NPS。相比于NPS，PS的稳定外延生长窗口更窄，需要更精确地调控生长参数，以实现高质量晶体的外延生长。

关键词: GaN晶体; Na助熔剂法; 图形化衬底; 非图形化衬底; 生长模式

Abstract: In this study， GaN crystals were grown by Na-flux liquid-phase epitaxy method on patterned substrates （PS） and non-patterned substrates （NPS） at various growth temperatures. COMSOL numerical simulations were employed to calculate and analyze the nitrogen concentration distribution and supersaturation evolution in the Ga-Na melt under different temperature conditions. The combined experimental and simulation results systematically reveal the differences in epitaxial growth behaviors of GaN crystals on PS and NPS. The results indicate that epitaxial growth on PS was successfully achieved only at 840 and 850 ℃. The obtained GaN crystals exhibit a regular hexagonal pyramid morphology， with partially unfilled gaps observed in the upper region of the cross-sections. As the temperature increases from 840 ℃ to 850 ℃， the nitrogen concentration in the melt increases while the supersaturation decreases， leading to smoother pyramid facets and an increase in crystal thickness from approximately 570 μm to 810 μm. When the temperature raises to 860 ℃， the supersaturation decreases further， resulting in complete dissolution of the seed points and no epitaxial growth occurring. In contrast， stable epitaxial growth on NPS was achieved over the temperature range from 840 ℃ to 860 ℃. With increasing temperature， the surface morphology evolves from ridge-like structures at lower temperatures to flat， cell-like structures at higher temperatures， while the cross-sections exhibit dense and laterally continuous growth. The crystal thickness first increases and then decreases with temperature increasing， reaching a maximum of approximately 1 450 μm at 850 ℃. In addition， the thickness of the GaN crystals obtained on PS is significantly thinner than that on NPS. Overall， compared with NPS， PS has a narrower stable epitaxial growth window， which requires more precise control of growth parameters to achieve high-quality epitaxial crystal growth.

Key words: GaN crystal; Na-flux method; patterned substrate; non-patterned substrate; growth mode

中图分类号:

O782⁺.1

黄戈萌, 马明, 夏颂, 范世, 李振荣. 图形化与非图形化薄膜衬底上Na助熔剂法生长GaN晶体的研究[J]. 人工晶体学报, 2026, 55(3): 411-422.

HUANG Gemeng, MA Ming, XIA Song, FAN Shiji, LI Zhenrong. GaN Crystals on Patterned and Non-Patterned Thin Film Substrates Grown by Na-Flux Method[J]. Journal of Synthetic Crystals, 2026, 55(3): 411-422.

图/表 15

图1 PS衬底示意图（a）及SEM照片（b）

Fig.1 Schematic diagram of PS substrate （a） and SEM image （b）

表1 实验工艺参数

Table 1 Experimental process parameters

No.	Mass fraction of raw material/%			Temperature/℃	Pressure/MPa	Time/h	Substrate
No.	Ga	Na	C	Temperature/℃	Pressure/MPa	Time/h	Substrate
a-1	30	70	0.5	840	3.5	96	PS
a-2	30	70	0.5	840	3.5	96	NPS
b-1	30	70	0.5	850	3.5	96	PS
b-2	30	70	0.5	850	3.5	96	NPS
c-1	30	70	0.5	860	3.5	96	PS
c-2	30	70	0.5	860	3.5	96	NPS

图2 籽晶放置三维计算模型

Fig.2 Three-dimensional computational model of seed crystal placement

表2 Ga-Na熔体的物性参数

Table 2 Physical properties of Ga-Na melt

Parameter	Value
Density， ρ/（kg·m^-3）	2 100
Thermal conductivity， $k$ /（W·m^-1·K^-1）	16.01
Dynamic viscosity， μ/（kg·m^-1·s^-1）	3.99×10^-4
Thermal expansion coefficient， $β T$ /K^-1	2.65×10^-4

表2 Ga-Na熔体的物性参数

Table 2 Physical properties of Ga-Na melt

Parameter	Value
Density， ρ/（kg·m^-3）	2 100
Thermal conductivity， $k$ /（W·m^-1·K^-1）	16.01
Dynamic viscosity， μ/（kg·m^-1·s^-1）	3.99×10^-4
Thermal expansion coefficient， $β T$ /K^-1	2.65×10^-4

图3 不同温度下不同衬底上外延生长GaN晶体的光学照片

Fig.3 Optical images of GaN crystals epitaxially grown on different substrates at different temperatures

图4 不同温度下外延生长GaN晶体的XRD图谱

Fig.4 XRD patterns of GaN crystals epitaxially grown at different temperatures

图5 840和850 ℃下不同衬底上外延生长的GaN晶体的表面SEM照片

Fig.5 Surface SEM images of GaN crystals epitaxially grown on different substrates at 840 and 850 ℃

图6 840和850 ℃下不同衬底上外延生长GaN晶体的断面SEM照片

Fig.6 Cross-sectional SEM images of GaN crystals epitaxially grown on different substrates at 840 and 850 ℃

图7 不同温度下不同衬底上外延生长GaN晶体的侧面SEM照片

Fig.7 Side SEM images of GaN crystals epitaxially grown on different substrates at different temperatures

图8 860 ℃下NPS上外延生长GaN晶体的SEM照片

Fig.8 SEM images of GaN crystal epitaxially grown on NPS at 860 ℃

图9 840和850 ℃下PS上外延生长GaN晶体的背面SEM照片

Fig.9 Backside SEM images of GaN crystals epitaxially grown on PS at 840 and 850 ℃

图10 不同温度下PS和NPS上外延生长GaN晶体的厚度

Fig.10 Thickness of GaN crystals epitaxially grown on PS and NPS at different temperatures

图11 不同温度下衬底表面附近宏观氮浓度分布

Fig.11 Macroscopic nitrogen concentration distribution near the substrate surface at different temperatures

图12 不同温度下衬底表面附近GaN过饱和度分布

Fig.12 Distribution of GaN supersaturation near the substrate surface at different temperatures

图13 不同衬底上外延生长GaN晶体的示意图

Fig.13 Schematic diagram of GaN crystals epitaxially grown on different substrates

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