Characterization and Electrical Property of Impurity Concentration in Ge-N Codoped SiC Crystals

doi:10.15541/jim20170256

Abstract

Abstract:

2-inch Ge-N codoped and Ge doped SiC single crystals were grown by physical vapor transport (PVT) method. And the SiC ingots were fabricated into 10 mm×10 mm SiC wafers for characterization. Semiconductor technology was used to fabricate Ti/Pt/Au metal contact on the carbide-terminated face of SiC wafers. Subsequently, all samples were characterized by secondary ion mass spectrometry (SIMS) and Hall measurements. The SIMS results showed that Ge-N codoping method could enhance the Ge doping concentration in SiC crystals effectively, which could achieve 1.19×10¹⁹/cm³. According to Hall measurement, ohmic contact could be obtained when samples were annealed at temperature higher than 700℃ and the optimal annealing temperature was 700℃. In addition, the contact resistance of the heavy Ge doped sample was lower than that of the light doped one, indicating that the ohmic contact property could be enhanced by improving the Ge doping concentrations in SiC crystals. Furthermore, as the increase of Ge doping concentration, the mobility gradually decreased. It was ascribed to that the Ge-N atoms matched well with SiC lattice in codoping method leading to higher Ge doping concentration. Under that condition, the impurity scattering effect became evident, which resulted in a lower mobility for Ge-N codoped sample.

Key words: Ge doping, lattice, Ohmic contact, mobility

CLC Number:

TB34

LI Tian, CHEN Xiu-Fang, YANG Xiang-Long, XIE Xue-Jian, ZHANG Fu-Sheng, XIAO Long-Fei, WANG Rong-Kun, XU Xian-Gang, HU Xiao-Bo, WANG Rui-Qi, YU Peng. Characterization and Electrical Property of Impurity Concentration in Ge-N Codoped SiC Crystals[J]. Journal of Inorganic Materials, 2018, 33(5): 535-539.

Figures/Tables 5

Fig. 1 SIMS analysis of Ge-N-codoped SiC substrate and Ge-doped SiC crystal substrate

Table 1 SiC crystal samples with different Ge-doping concentrations

Sample	Structure	Ge doping concentration/cm^-3
A	Ti/Pt/Au/SiC	Undoped
B	Ti/Pt/Au/Ge-SiC	~5×10¹⁷
C	Ti/Pt/Au/Ge-SiC	9.39×10¹⁸
D	Ti/Pt/Au/Ge-SiC	1.19×10¹⁹

Fig. 2 I-V curves of sample C annealed at different temperatures

Fig. 3 I-V curves of different samples annealed at 700℃

Fig. 4 Mobility curve of different Ge-doping concentration SiC crystal samples

References 28

[1]	CASADY J B, JOHNSON R W.Status of silicon carbide (SiC) as a wide-bandgap semiconductor for high-temperature applications: a review.Solid-State Electronics, 1996, 39(10): 1409-1422.
[2]	ITOH A, MATSUNAMI H.Single crystal growth of SiC and electronic devices.Critical Reviews in Solid State and Material Sciences, 1997, 22(2): 111-197.
[3]	BHATNAGAR M, BALIGA B J.Comparison of 6H-SiC, 3C-SiC, and Si for power devices.IEEE Transactions on Electron Devices, 1993, 40(3): 645-655.
[4]	ROST H J, DOERSCHEL J, IRMSCHER K,et al. Influence of nitrogen doping on the properties of 4H-SiC single crystals grown by physical vapor transport. Journal of Crystal Growth, 2003, 257(1): 75-83.
[5]	UEMOTOU T.Reduction of ohmic contact resistance on n-type 6H-SiC by heavy doping.Japanese Journal of Applied Physics, 1995, 34(1A): L7.
[6]	STRAUBINGER T L, BICKERMANN M, WEINGÄRTNER R,et al. Aluminum p-type doping of silicon carbide crystals using a modified physical vapor transport growth method. Journal of Crystal Growth, 2002, 240(1): 117-123.
[7]	MÜLLER R, KÜNECKE U, WEINGÄRTNER R,et al. High Al-doping of SiC using a modified PVT (M-PVT) growth set-up. Materials Science Forum. Trans. Tech. Publications, 2005, 483: 31-34.
[8]	BICKERMANN M, HOFMANN D, RASP M,et al. Study of boron incorporation during PVT growth of p-type SiC crystals. Materials Science Forum. Trans Tech Publications, 2001, 353: 49-52.
[9]	ZHANG FU-SHENG, CHEN XIU-FANG, CUI YING-XIN,et al. Defects in Ge doped SiC crystals. Journal of Inorganic Materials, 2016, 31(11): 1166-1170.
[10]	ROE K J, DASHIELL M W, XUAN G, et al. Ge incorporation in SiC and the effects on device performance. High Performance Devices, 2002. Proceedings. IEEE Lester Eastman Conference on. IEEE, 2002: 201-206.
[11]	GHOSH A, VARADACHARI C.Theoretical derivations of a direct band gap semiconductor of SiC doped with Ge.Journal of Electronic Materials, 2015, 44(1): 167.
[12]	ZANG YUAN, CAO LIN, LI LIAN-BI,et al. Theoretical study of electrical and optical properties of Ge-doped 6H-SiC. Laser & Optoelectronics Progress, 2015, 52(6): 209-215.
[13]	CHEN J S, BACHLI A, NICOLET M A,et al. Contact resistivity of Re, Pt and Ta films on n-type β-SiC: preliminary results. Materials Science and Engineering: B, 1995, 29(1/2/3): 185-189.
[14]	KONISHI R, YASUKOCHI R, NAKATSUKA O,et al. Development of Ni/Al and Ni/Ti/Al ohmic contact materials for p-type 4H-SiC. Materials Science and Engineering: B, 2003, 98(3): 286-293.
[15]	OHYANAGI T, ONOSE Y, WATANABE A.Ti/Ni bilayer Ohmic contact on 4 H-Si C.Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2008, 26(4): 1359-1362.
[16]	CHONG-CHONG D, XUE-CHAO L, TIAN-YU Z,et al. Effects of annealing temperature on the electrical property and microstructure of aluminum contact on n-type 3C—SiC. Chinese Physics B, 2014, 23(6): 066803.
[17]	DAI C C, LIU X C, ZHOU T Y,et al. Effect of annealing temperature on the contact properties of Ni/V/4H-SiC structure. AIP Advances, 2014, 4(4): 047125.
[18]	TIAN-YU Z, XUE-CHAO L, WEI H,et al. Electrical properties and microstructural characterization of Ni/Ta contacts to n-type 6H-SiC. Chinese Physics B, 2015, 24(12): 126801.
[19]	ZHOU T Y, LIU X C, DAI C C,et al. Effect of graphite related interfacial microstructure created by high temperature annealing on the contact properties of Ni/Ti/6H-SiC. Materials Science and Engineering: B, 2014, 188: 59-65.
[20]	CROFTON J, BARNES P A, WILLIAMS J R,et al. Contact resistance measurements on p-type 6H-SiC. Applied Physics Letters, 1993, 62(4): 384-386.
[21]	CROFTON J, BEYER L, WILLIAMS J R,et al. Titanium and aluminum-titanium ohmic contacts to p-type SiC. Solid-State Electronics, 1997, 41(11): 1725-1729.
[22]	CHANG S C, WANG S J, UANG K M,et al. Investigation of Au/Ti/Al ohmic contact to N-type 4H-SiC. Solid-state electronics, 2005, 49(12): 1937-1941.
[23]	LEE C T, KAO H W.Long-term thermal stability of Ti/Al/Pt/Au Ohmic contacts to n-type GaN.Applied Physics Letters, 2000, 76(17): 2364-2366.
[24]	ZHOU L, LANFORD W, PING A T,et al. Low resistance Ti/Pt/Au ohmic contacts to p-type GaN. Applied Physics Letters, 2000, 76(23): 3451-3453.
[25]	YANG KUN, CHEN XIU-FANG, YANG XIANG-LONG,et al. Growth of high purity semi-insulting 4H-SiC single crystals. Journal of Synthetic Crystals, 2014, 43(11): 3055-3057.
[26]	LARKIN D J, NEUDECK P G, POWELL J A,et al. Site-competition epitaxy for superior silicon carbide electronics. Applied Physics Letters, 1994, 65(13): 1659-1661.
[27]	XU M, HU X, PENG Y,et al. Fabrication of ohmic contact on the carbon-terminated surface of n-type silicon carbide. Journal of Alloys and Compounds, 2013, 550: 46-49.
[28]	JOHNSON B J, CAPANO M A.Mechanism of ohmic behavior of Al/Ti contacts to p-type 4H-SiC after annealing.Journal of Applied Physics, 2004, 95(10): 5616-5620.