Research On Optically Controlled THz Wave Modulation Device Based On Semiconductor

THz wave has many excellent characteristics,such as high frequency broadband,low energy,high time resolution,etc.,making it of great application value in the fields of wireless communication,security inspection and defect inspection.In these terahertz application scenarios,terahertz wave modulation technology is very important.Among the existing modulation devices,semiconductor control devices occupy an important position.Silicon-based devices have received the most attention among them,but silicon is limited by its carrier lifetime and it is difficult to achi e Ve rapid response to terahertz waves.Gallium arsenide has a short carrier life and can be used to manufacture modulation devices that respond quickly to terahertz waves.How e Ver,the gallium arsenide-based modulator requires a large laser excitation signal energy,which is not conducive to application and promotion.In addition,germanium has so a low forbidden band width that can efficiently use the laser with a wavelength of 1550 nm,and facilitate integration with existing optical fiber communication systems.The surface density of states seriously affects the performance of semiconductor devices.The focus of this paper is how to improve the modulation depth of GaAs-based and Ge-based optically controlled terahertz wave modulators.The influence of surface passivation technology on the modulation depth of GaAs-based and Ge-based optically controlled terahertz wave modulators is studied.First,the influence of surface passivation technology on the modulation performance of GaAs-based terahertz wave modulators is studied.The surface of GaAs is etched by H₂SO₄ solution,and the PL lu minescence intensity is increased by 2.5 times;GaAs is passivated by sulfur on the surface of(NH4)2S solution,and the room temperature PL test shows that the best passivation time of the sample is at 20 minutes,the lu minescence intensity of the sample increased by about 7 times,indicating that the GaAs surface state density decreased and the surface recombination rate decreased.The OPTP test shows that under the action of 800 nm femtosecond laser pumping,the modulation depth of the THz wave of GaAs after acid etching and sulfur passivation at 3 mW increased by 11%and 16%,respectively,compared with that of bare GaAs.At the same time,the stability is greatly improved.How e Ver the effect of sulfur passivation is unstable in the air.Then,a 96.3 nm thick Al₂O₃ film is deposited on the sulfur passivated GaAs by magnetron sputtering,which can not only improve the stability of sulfur passivation,but also increase the utilization rate of the laser.The test shows that under the action of 800 nm femtosecond laser pump,the Al₂O₃ film GaAs deposited after sulfur passivation at 3 mW modulates the Thz wave depth by 12%compared with bare GaAs.Secondly,the influence of surface passivation technology on the modulation performance of germanium-based terahertz wave modulators is studied.The germanium surface is passivated through a mixed solution of HF and H₂O₂,and the germanium surface is field passivated through a single-layer graphene.Both passivation methods have greatly improved the modulation performance of the modulator.Fico test find that under the action of 1550 nm laser pump,when the laser power is 200 mW,the modulator modulation depth of HF and H₂O₂ passivated with graphene are 80%and 83%respectively,which is 31%more than bare germanium,34%.Next,the effects of HF and H₂O₂ and graphene dual passivation methods on the modulation performance of germanium-based terahertz wave modulators are studied.The test find that under the action of 1550 nm laser pump,when the laser power is 200 mW,the modulation depth of the modulator after double passivation is 70%,which is 21%higher than that of bare germanium.The research of semiconductor surface passivation technology began in the last century,but its research in the field of THz is rarely seen in the literature.This paper studies the influence of surface chemical passivation technology on the modulation depth of GaAs-based and Ge-based optically controlled terahertz wave modulators,enriching the research of semiconductor material surface chemical passivation technology in the field of optically controlled THz modulators and providing a new way of selection to achi e Ve the high efficiency THz modulator.