Raman Spectroscopy Study on the Influence of Different Dislocations on Carrier Concentration in 4H-SiC

doi:10.16553/j.cnki.issn1000-985x.2025.0219

Abstract

Abstract: The n-type 4H-SiC crystal samples prepared by the physical vapor transport （PVT） method in this study were subjected to etching treatment using molten KOH in a nickel crucible at 520 ℃. Dislocations in the wafer， including threading edge dislocation （TED）， threading screw dislocation （TSD）， and threading mixed dislocation （TMD）， were distinguished and identified using optical microscopy （OM）， atomic force microscopy （AFM）， and scanning electron microscopy （SEM）. Micro-Raman spectroscopy was employed to characterize the spectral features of these different dislocation defects. The Raman spectra from the defect regions were compared with those from defect-free regions， with particular focus on the longitudinal optical phonon plasmon coupling （LOPC） mode near 984.609 cm^-1， which is influenced by increased carrier concentration. The Raman spectra were fitted using Matlab， and the carrier concentration （n） in different regions was calculated based on theoretical formulas. Comparing the n values at the defect cores with those in defect-free areas revealed a significant carrier trapping effect at the defect cores. The full width at half maximum （FWHM） of the Raman spectra at each defect core was further calculated. By jointly analyzing the FWHM and the carrier concentration n， the relative strength of the carrier trapping effect for different dislocation types was assessed， yielding the following order： TSD， TMD， TED. Some optimization suggestions are proposed for the crystal growth process and device fabrication process.

Key words: SiC crystal; carrier concentration; detect; dislocation; Raman spectra; carrier trapping effect

CLC Number:

ZHUANG Changyu, WU Meixia, QUAN Jiliang, LI Shuti. Raman Spectroscopy Study on the Influence of Different Dislocations on Carrier Concentration in 4H-SiC[J]. Journal of Synthetic Crystals, 2026, 55(3): 403-410.

Figures/Tables 9

Fig.1 OM images of corrosion pits

Fig.2 SEM images of corrosion pits

Fig.3 AFM images and cross-sectional curves of corrosion pits

Fig.4 Raman spectrum of defect-free region

Table 1 Comparison of sample peak positions with standard peak positions

Peak position	FTA	FLA	FTO， E₂	FTO， E₁	FLO
Sample peak position/cm^-1	203.23	609.608	776.215	797.404	984.609
Standard peak position/cm^-1	203	610	776	796	964

Fig.5 Raman spectra of center and surrounding defect-free region

Fig.6 Raman spectra compared for TED， TSD and TMD defect centers

Table 2 Material constant values of 4H-SiC［29］

Material constant	Value
LO phonon，ω_L/cm^-1	964.2
TO phonon， ω_T/cm^-1	777.0
Faust-Henry constant， C	0.43
Optical dielectric constant， ε_∞	6.78
Carrier effective mass， m^*	0.48m₀（m₀=9.11×10^-31 kg）

Table 3 Carrier concentration and FWHM at defect centers of TED， TSD and TMD

Parameter	TED-C	TSD-C	TMD-C	Hall
n/cm^-3	6.54×10¹⁷	3.43×10¹⁸	7.21×10¹⁷	4.83×10¹⁸
FWHM/cm^-1	3.92	6.25	5.65

References 30

[1]	MATSUNAMI H. Fundamental research on semiconductor SiC and its applications to power electronics［J］. Proceedings of the Japan Academy Series B， Physical and Biological Sciences， 2020， 96（7）： 235-254.
[2]	KIMOTO T， WATANABE H. Defect engineering in SiC technology for high-voltage power devices［J］. Applied Physics Express， 2020， 13（12）： 120101.
[3]	KIMOTO T. Bulk and epitaxial growth of silicon carbide［J］. Progress in Crystal Growth and Characterization of Materials， 2016， 62（2）： 329-351.
[4]	ZHANG J R， LIANG T， LU Y H， et al. Effect of hexagonality on the pressure-dependent lattice dynamics of 4H-SiC［J］. New Journal of Physics， 2022， 24（11）： 113015.
[5]	王　宇，顾　鹏，付　君，等. PVT法生长4H-SiC晶体及多型夹杂缺陷研究进展［J］. 人工晶体学报， 2022， 51（12）： 2137-2152.
	WANG Y， GU P， FU J， et al. Research progress on the growth of 4H-SiC crystal by PVT method and the defect of polytype inclusions［J］. Journal of Synthetic Crystals， 2022， 51（12）： 2137-2152 （in Chinese）.
[6]	杨　光，刘晓双，李佳君，等. 4H碳化硅单晶中的位错［J］. 人工晶体学报， 2022， 51（增刊）： 1673-1690.
	YANG G， LIU X S， LI J J， et al. Dislocation in 4H silicon carbide single crystal［J］. Journal of Synthetic Crystals， 2022， 51（supplement）： 1673-1690 （in Chinese）.
[7]	MAXIMENKO S I， PIROUZ P， SUDARSHAN T S. Investigation of the electrical activity of partial dislocations in SiC p-i-n diodes［J］. Applied Physics Letters， 2005， 87（3）： 033503.
[8]	GALECKAS A， LINNROS J， PIROUZ P. Recombination-induced stacking faults： evidence for a general mechanism in hexagonal SiC［J］. Physical Review Letters， 2006， 96（2）： 025502.
[9]	DAS S， ZHENG Y， AHYI A， et al. Study of carrier mobilities in 4H-SiC MOSFETS using Hall analysis［J］. Materials， 2022， 15（19）：6736.
[10]	CALCAGNO L， RAINERI V. Depth carrier profiling in silicon carbide［J］. Current Opinion in Solid State and Materials Science， 2002， 6（1）： 47-54.
[11]	TAKANORI T， SHIGEHISA， YU N， et al. Silicon carbide epitaxial substrate and silicon carbide semiconductor device［EB/OL］. Mitsubishi Electric Corp， 2020. .
[12]	WANG L， PARK B S. SIMS analysis of nitrogen in silicon carbide using raster change technique［J］. MRS Online Proceedings Library， 2011， 911（1）： 508.
[13]	NAKASHIMA S， HARIMA H. Characterization of defects in SiC crystals by Raman scattering［M］//silicon carbide： recent major advances. Berlin， Heidelberg： Springer Berlin Heidelberg， 2004： 585-605.
[14]	HARIMA H， NAKASHIMA S I， UEMURA T. Raman scattering from anisotropic LO-phonon-plasmon-coupled mode in n-type 4H- and 6H-SiC［J］. Journal of Applied Physics， 1995， 78（3）： 1996-2005.
[15]	LIN S H， CHEN Z M， LI L B， et al. Investigation of micropipes in 6H-SiC by Raman scattering［J］. Physica B： Condensed Matter， 2012， 407（4）： 670-673.
[16]	FENG X F， ZANG Y. Raman scattering properties of structural defects in SiC［C］//Proceedings of the 2016 3rd International Conference on Mechatronics and Information Technology. April 9-10， 2016. Shenzhen， China， PressAtlantis， 2016： 829-835.
[17]	苗瑞霞. n型4H-SiC材料中位错的电学特性研究［J］. 半导体光电， 2015， 36（4）： 574-576+591.
	MIAO R X. Study on dislocation electrical properties in n-type 4H-SiC material［J］. Semiconductor Optoelectronics， 2015， 36（4）： 574-576+591 （in Chinese）.
[18]	刘　涛. 碳化硅载流子浓度的拉曼光谱表征研究［D］. 天津：天津大学， 2020.
	LIU T. Research on the Raman characterization of carriers concentration of silicon carbide［D］. Tianjin： Tianjin University， 2020 （in Chinese）.
[19]	王光红，施成营，冯　敏，等. 拉曼光谱研究n型4H-和6H-SiC晶体的载流子浓度［J］. 光散射学报， 2007， 19（2）： 108-113.
	WANG G H， SHI C Y， FENG M， et al. Characterization of the free-carrier concentrations in doped n-type 4H-and 6H-SiC crystals by Raman scattering［J］. The Journal of Light Scattering， 2007， 19（2）： 108-113 （in Chinese）.
[20]	KATSUNO M， OHTANI N， TAKAHASHI J， et al. Etching kinetics of α-SiC single crystals by molten KOH［J］. Materials Science Forum， 1998， 264/265/266/267/268： 837-840.
[21]	YAO Y Z， ISHIKAWA Y， SUGAWARA Y， et al. Molten KOH etching with Na₂O₂ additive for dislocation revelation in 4H-SiC epilayers and substrates［J］. Japanese Journal of Applied Physics， 2011， 50（7R）： 075502.
[22]	YANG G， LUO H， LI J J， et al. Discrimination of dislocations in 4H-SiC by inclination angles of molten-alkali etched pits［J］. Journal of Semiconductors， 2022， 43（12）： 122801.
[23]	王守国，柴泾睿，王　登. 4H-SiC同质外延拉曼散射光谱［J］. 西北大学学报（自然科学版）， 2015， 45（2）： 229-232.
	WANG S G， CHAI J R， WANG D. A study on Raman scattering spectra of 4H-SiC homoepitaxial layers［J］. Journal of Northwest University （Natural Science Edition）， 2015， 45（2）： 229-232 （in Chinese）.
[24]	綦正超，许庭翔，刘学超，等. 杂质和缺陷对SiC单晶导热性能的影响［J］. 人工晶体学报， 2021， 50（5）： 816-824.
	QI Z C， XU T X， LIU X C， et al. Effect of impurities and defects on the thermal conductivity of single crystal SiC［J］. Journal of Synthetic Crystals， 2021， 50（5）： 816-824 （in Chinese）.
[25]	CHEN S， WAN L Y， XIE D， et al. Adducing crystalline features from Raman scattering studies of cubic SiC using different excitation wavelengths［J］. Journal of Physics D Applied Physics， 2017， 50（11）： 115102.
[26]	KLEIN M V， GANGULY B N， COLWELL P J. Theoretical and experimental study of Raman scattering from coupled LO-phonon-plasmon modes in silicon carbide［J］. Physical Review B， 1972， 6（6）： 2380-2388.
[27]	YUGAMI H， NAKASHIMA S， MITSUISHI A， et al. Characterization of the free-carrier concentrations in doped β-SiC crystals by Raman scattering［J］. Journal of Applied Physics， 1987， 61（1）： 354-358.
[28]	COLWELL P J， KLEIN M V. Raman scattering from electronic excitations in n-type silicon carbide［J］. Physical Review B， 1972， 6（2）： 498-515.
[29]	PERSSON C， LINDEFELT U. Relativistic band structure calculation of cubic and hexagonal SiC polytypes［J］. Journal of Applied Physics， 1997， 82（11）： 5496-5508.
[30]	NAKASHIMA S， HARIMA H. Raman investigation of SiC polytypes［J］. Physica Status Solidi （a）， 1997， 162（1）： 39-64.