THz System on Chip Based on LT-GaAs Epitaxial Chip
WU Rui, SU Bo*, ZHAO Ya-ping, HE Jing-suo, ZHANG Sheng-bo, ZHANG Cun-lin
Key Laboratory of Terahertz Optoelectronics, Ministry of Education; Beijing Key Laboratory for Terahertz Spectroscopy and Imaging; Beijing Advanced Innovation Center for Imaging Theory and Technology, Department of Physics, Capital Normal University, Beijing 100048, China
Abstract：Terahertz (THz) waves play an important role in material detection and is a potential biochemical sensor. However, the traditional terahertz time-domain spectroscopy (THz-TDS) system is complex in structure, low in integration and large in space. Therefore, guiding THz wave effectively, realising integrated transmission, and getting high-quality spectroscopy has become a research hotspot of the terahertz spectroscopy system. THz system on chip integrates the generation, transmission and detection of THz on the same chip, and then obtains THz time-domain spectroscopy by coherent detection. It can be used to detect many kinds of samples, especially in detecting trace samples thatare difficult to sample. It does notneed optical alignment, is easy to operate and has a high yield. The two research works in this paper are based on low-temperature GaAs (LT-GaAs) epitaxial wafers. Firstly, a 200 μm diameter copper wire is fixed on the top of the LT-GaAs epitaxial wafer, and the antenna electrode is prepared by vacuum evaporation. At the same time, the antenna gap is obtained, and the THz antenna based on the LT-GaAs epitaxial wafer is developed. The high-quality THz signal is obtained by using the femtosecond laser with a wavelength of 800 nm, which verifies the practicability of the antenna. Then the transmission line and microelectrode are fabricated on another epitaxial wafer by lithography, and the integrated THz system on chip is obtained. A femtosecond laser with a wavelength of 1 550 nm is used to excite the terahertz generation antenna and the system’s detection antenna on chip. The THz waves generated by the antenna propagate on the transmission line, and the high-quality THz time-domain signal is also obtained at the detection end, which proves the feasibility of the system achip. This method omits the steps of corrosion sacrificial layer, transfer and bonding of LT-GaAs film greatly improves the yield of the system a chip, and avoids the problems of fragility and toxicity of corrosive solutionthe process of film transfer. Finally, the influence of applied voltage on THz wave performance obtained from the system on chip is studied. The results show that the higher the voltage is, the stronger THz wave’ssignal strength is. Besides, the fact that THz waves propagate along the transmission line is verified by placing copper foil vertically above the transmission line. The system on chip based on LT-GaAs epitaxial wafer used in this study has the advantages of simple preparation method, short fabrication cycle, safe fabrication process and wide application field, which lays a foundation for detecting liquid samples by combining with microfluidic chips in the future.
Key words：Terahertz; Epitaxial wafer; LT-GaAs; Photoconductive antenna; System on chip
[1] ZHAO Xing-hai, BAO Jing-fu, DU Yi-jia, et al（赵兴海，鲍景富，杜亦佳，等）. Transducer and Microsystem Technologies（传感器与微系统），2011，(7): 5.
[2] GUAN Ai-hong, CHAO Yong-yang, LI Zhi（管爱红，晁永阳，李 智）. China Food Additives（中国食品添加剂），2019, (1): 149.
[3] Wood C, Cunningham J, Hunter I C, et al. International Journal of Infrared & Millimeter Waves, 2006, 27(4): 557.
[4] Russell, Christopher. University of Leeds（利兹大学），2013.
[5] Yutaka Kadoya, et al. 19th International Conference on Applied Electromagnetics and Communications, Dubrovnik, 2008, 17(2): 48.
[6] Treizebre A, Laurette S, Xu Y, et al. Progress in Electromagnetics Research C, 2012, 26: 219.
[7] Horibe M, Kishikawa R. IEEE Transactions on Instrumentation & Measurement, 2013, 62(6): 1814.
[8] Yanagi S, Onuma M, Kitagawa J, et al. Applied Physics Express, 2008, 1(1): 012009.
[9] Matheisen C, Nagel M, Sawallich S. International Conference on Infrared. Millimeter and Terahertz Waves IEEE, 2015.
[10] ZHANG Cong, SU Bo, ZHANG Hong-fei, et al（张 聪，苏 波，张宏飞，等）. Spectroscopy and Spectral Analysis（光谱学与光谱分析），2019, 39(10): 3308.
[11] GUO Chun-yan, XU Jian-xing, PENG Hong-ling, et al（郭春妍，徐建星，彭红玲，等）. Journal of Infrared and Millimeter Waves（红外与毫米波学报）, 2017, (2): 220.
[12] LI Zhong-xiao, XU De-gang, WANG Yu-ye, et al（李忠孝，徐德刚，王与烨, 等）. Journal of Optoelectronics·Laser（光电子·激光）, 2015，(1): 177.
[13] LAI Wu-xing, XUAN Jian-ping, SHI Tie-lin, et al（来五星，轩建平，史铁林，等）. Semiconductor Technology（半导体技术），2004，(11): 22.
[14] Erlig H, Wang S, Azfar T, et al. Proceedings of SPIE, 1999, 3795: 338.
[15] Sakai K, Tani M. Oyobuturi（应用物理）, 2001, 70: 149.
[16] HUANG Rui-rui, ZHAO Guo-zhong, LIU Ying, et al（黄瑞瑞，赵国忠，刘 影，等）. Acta Optica Sinica（光学学报）, 2015，(A02): 228.
[17] Denlinger E J. IEEE Transactions on Microwave Theory & Techniques, 1980, 28(6): 513.
[18] Huang Y, Khiabani N, Shen Y, et al. 2011 International Workshop on Antenna Technology, Hong Kong, 2011. 152.
