Performance of Lateral 4H-SiC Photoconductive Semiconductor Switches by Extrinsic Backside Trigger

doi:10.15541/jim20240136

Abstract

Abstract:

Photoconductive semiconductor switch (PCSS) can be applied in pulsed high power systems and microwave techniques. However, reducing the damage and increasing the lifetime of silicon carbide (SiC) PCSS are still faced severe challenges. In this study, PCSSs with various structures were prepared on 4-inch diameter, 500 μm thick high-purity semi-insulating 4H-SiC substrates and their on-state resistance and damage mechanisms were investigated. It was found that the PCSS of an Au/TiW/Ni electrode system annealed at 950 ℃ had a minimum on-state resistance of 6.0 Ω at 1 kV bias voltage with a 532 nm and 170 mJ pulsed laser by backside illumination single trigger. The backside illumination single trigger could reduce on-state resistance and alleviate the damage of PCSS compared to the frontside trigger when the diameter of the laser spot was larger than the channel length of PCSS. For the 200 s trigger test by a 10 Hz laser, the black branch-like ablation on Au/TiW/Ni PCSS was mainly caused by thermal stress owing to hot carriers. Replacing metal Ni with boron gallium co-doped zinc oxide (BGZO) thin films annealed at 400 ℃, black branch-like ablation was alleviated while concentric arc damage was obvious at the anode. The major causes of concentric arc are both pulsed laser diffraction and thermal effect.

Key words: silicon carbide, photoconductive semiconductor switch, on-state resistance, failure analysis

CLC Number:

TN36

WANG Hao, LIU Xuechao, ZHENG Zhong, PAN Xiuhong, XU Jintao, ZHU Xinfeng, CHEN Kun, DENG Weijie, TANG Meibo, GUO Hui, GAO Pan. Performance of Lateral 4H-SiC Photoconductive Semiconductor Switches by Extrinsic Backside Trigger[J]. Journal of Inorganic Materials, 2024, 39(9): 1070-1076.

Figures/Tables 10

Fig. 1 Basic fabrication flowchart of SiC PCSS

Fig. 2 Diagrams of SiC PCSS electrodes components (a) Au/TiW/Ni/SiC; (b) Au/TiW/BGZO/SiC

Fig. 3 Schematic diagram of PCSS testing circuit

Fig. 4 Comparison of on-state resistance of SiC1_Ni and SiC2_Ni PCSS by FSI and BSI single trigger

Fig. 5 Electrode damage microscope images of SiC2_Ni PCSS after FSI and BSI single trigger tests (a) Anode FSI; (b) Cathode FSI; (c) Cathode BSI; (d) Anode BSI

Fig. 6 Output peak voltage plots of SiC PCSSs by multiple triggers (a) SiC1_Ni; (b) SiC2_Ni; (c) SiC1_BGZO; (d) SiC2_BGZO

Table 1 GDMS results of SiC1 and SiC2

Element	SiC1/(μg·g^-1)	SiC2/(μg·g^-1)
B	3.2	3.0
Al	41	22
V	<0.05	<0.05

Fig. 7 SEM images of SiC1_Ni PCSS damage after multiple triggers tests (a) Cathode; (b) Anode

Table 2 EDS results of SiC1_Ni PCSS

Element	Residual metal/(%, in atom)	Ablation/(%, in atom)
C	53.41	55.91
O	BDL	1.31
Si	13.85	42.42
Ti	2.03	BDL
Ni	11.14	0.25
W	7.41	BDL
Au	12.17	0.10

Fig. 8 Microscope images on electrode damage of SiC1_BGZO PCSS after trigger tests (a) Cathode and (b) anode after a single trigger test; (c) Cathode and (d) anode after multiple triggers

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