光电导体中瞬态空间电荷电场对光电导开关及THz光电导偶极天线的影响
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摘要
THz作为电磁波谱中至今仍然未被人们开发利用的波段，已经被众多的科学工作者所关注。其独特的性质能够给成像技术、生物医学、通讯、国防等高科技领域带来巨大的影响。光电导开关作为兼顾脉冲功率和带宽的微波源，在THz电磁波的产生方面以及功率脉冲技术领域具有独特的优势。光电导体中的载流子在光电导体内的运动情况决定了所输出电脉冲的波形，而载流子的运动是在光电导体内部电场的作用下进行的，所以光电导体内的电场对光电导开关的性能有显著的影响。光电导体内的电场是偏置电场、光电导体内光生载流子的空间瞬态分布所形成的空间电荷电场等叠加形成的合电场。偏置电场在光电导过程中变化较小，对载流子运动的作用稳定。而空间电荷电场随着载流子的空间位置的变化而变化，并同时影响载流子的瞬间运动状态，其变化复杂，并且对载流子运动的影响不容忽视。在触发光功率较大的条件下，空间电荷电场对载流子的运动影响是十分显著的。触发条件下光电导体内部电场不仅显著的影响光电导开关产生超快电脉冲的功率、波形，而且对THz偶极天线的辐射功率也有明显的影响。本文利用计算机时域有限分析方法，模拟了光电导体内的瞬态电场，揭示了光电导体在超短脉冲激光触发下内部电场的形成和变化情况。结果表明在触发光功率较大的条件下，光电导体内存在多个电荷畴。
通过对模拟结果的分析，根据载流子的运动特性的不同，对光电导开关的工作模式进行了细化分类。通过对THz光电导天线中瞬态电场的模拟，得到了芯片内瞬
西安理工大学硕士学位论文
态电流的变化曲线，并通过FDTD方法对瞬态电流模拟结果进行了验证。分析了瞬
态电场对THz偶极天线辐射的影响。
本文还通过实验研究了钝化工艺对THz偶极天线辐射功率的影响。与未钝化的
光电导偶极天线相比，Si3N;钝化过的光电导偶极天线耐压能力显著提高，其辐射功
率约为未钝化天线的1.5倍。另外，在新型光电导天线的研究方面，设计了缝隙天线
与光电导偶极天线结合的新型THz天线。
As an wave-band in the electromagnetic spectrum which hardly being used to this day, terahertz has came to be a focus to scientists of all over the would. Because of it's unique character, THz may give prominent influence to the field of imaging, biology, communication, national-defense and so on. Being a source of microwave it is provided with merit of power and bandwidth at the same time, photoconductive semiconductor switches has unique predominance in the field of power pulse technology and THz sources. Carries created by ultra-fast laser pulse accelerate in the field of the photoconductor and form a transient photocurrent. The shape of the photocurrent lies on the movement of the carriers, as well as the movement of the carrier's lies on the field in the photoconductor. The field in large-aperture photoconductors is mainly composed of bias field, space-charge field formed by transient distributing of carriers. Bias field is comparatively static, so the influence to carriers is static too. Oppositely, sp
ace-charge field changes along with the movement of the carriers, and influences the movement of carriers synchronously. It's an intricate process and can not to be ignored in PCSS's. In the case of triggering by high power optical, space-charge field can intensity influence the movement of the carrier. Thus, space-charge field in excitated photoconductor can intensity influence not only the shape of photo-electric current of PCSS's, but also the terahertz out put of photoconducting antenna. In this paper, the forming and movement of space-charge field are simulated by means of FDTD method. And the result of simulate indicates that several charge domains could exist in photoconductor at the same time.
In this paper, through analyzing of the result of simulation, the working model of PCSS's was particular classed based on the movement of the carriers. By simulating of transient field in the photoconductor of THz photoconductive antenna, the curve of instant electric current was given here, and the result was validated by FDTD method. The influence of transient field to THz out put was mentioned in this paper too.
THz radiation generated from a Si3N4 covered GaAs photoconductive dipole antenna is investigated in the paper. Comparing with uncovered antennas with the same gap size, the covered antenna has higher breakdown voltage at the same optical exciting power, and it's THz out put is 1.5 times of uncovered antenna.
通过对模拟结果的分析，根据载流子的运动特性的不同，对光电导开关的工作模式进行了细化分类。通过对THz光电导天线中瞬态电场的模拟，得到了芯片内瞬
西安理工大学硕士学位论文
态电流的变化曲线，并通过FDTD方法对瞬态电流模拟结果进行了验证。分析了瞬
态电场对THz偶极天线辐射的影响。
本文还通过实验研究了钝化工艺对THz偶极天线辐射功率的影响。与未钝化的
光电导偶极天线相比，Si3N;钝化过的光电导偶极天线耐压能力显著提高，其辐射功
率约为未钝化天线的1.5倍。另外，在新型光电导天线的研究方面，设计了缝隙天线
与光电导偶极天线结合的新型THz天线。
As an wave-band in the electromagnetic spectrum which hardly being used to this day, terahertz has came to be a focus to scientists of all over the would. Because of it's unique character, THz may give prominent influence to the field of imaging, biology, communication, national-defense and so on. Being a source of microwave it is provided with merit of power and bandwidth at the same time, photoconductive semiconductor switches has unique predominance in the field of power pulse technology and THz sources. Carries created by ultra-fast laser pulse accelerate in the field of the photoconductor and form a transient photocurrent. The shape of the photocurrent lies on the movement of the carriers, as well as the movement of the carrier's lies on the field in the photoconductor. The field in large-aperture photoconductors is mainly composed of bias field, space-charge field formed by transient distributing of carriers. Bias field is comparatively static, so the influence to carriers is static too. Oppositely, sp
ace-charge field changes along with the movement of the carriers, and influences the movement of carriers synchronously. It's an intricate process and can not to be ignored in PCSS's. In the case of triggering by high power optical, space-charge field can intensity influence the movement of the carrier. Thus, space-charge field in excitated photoconductor can intensity influence not only the shape of photo-electric current of PCSS's, but also the terahertz out put of photoconducting antenna. In this paper, the forming and movement of space-charge field are simulated by means of FDTD method. And the result of simulate indicates that several charge domains could exist in photoconductor at the same time.
In this paper, through analyzing of the result of simulation, the working model of PCSS's was particular classed based on the movement of the carriers. By simulating of transient field in the photoconductor of THz photoconductive antenna, the curve of instant electric current was given here, and the result was validated by FDTD method. The influence of transient field to THz out put was mentioned in this paper too.
THz radiation generated from a Si3N4 covered GaAs photoconductive dipole antenna is investigated in the paper. Comparing with uncovered antennas with the same gap size, the covered antenna has higher breakdown voltage at the same optical exciting power, and it's THz out put is 1.5 times of uncovered antenna.
引文
[1] Peter H. Siegel. Terahertz Technology. IEEE Transactions on Microwave Theory AND Techniques VOL. 50, NO. 3, March 2002: 910～928
[2] Bradley Ferguson And Xi-Cheng ZHANG. Materials for Terahertz Science and Technology. Nature Materials Vol: 1, SEPTEMBER 2002: 26～33.
[3] 王少宏、许景周、汪力、张希成．THz技术的应用及展望．物理 30(10)，2001：612～615
[4] Joel E. Boyd, Ari Briskman, Christie M. Sayes, Daniel Mittleman, and Vicki Colvin. Terahertz Vibrational Modes of Inverse Micelles. J. Phys. Chem. B 2002, 106, 2002: 6346～6353
[5] Daniel M. Mittleman, Stefan Hunsche, Luc Boivin, and Martin C. Nuss. T-ray tomography. OPTICS LETTERS, Vol. 22, No. 12 June 15, 1997: 904～906
[6] R. H. Jacobsen, D. M. Mittleman, and M. C. Nuss. Chemical recognition of gases and gas mixtures with terahertz waves. OPTICS LETTERS, Vol. 21, No. 24, December 15, 1996: 2011～2013.
[7] D.L. Woolard, T. Koscica AND D.L.Rhodes, Millimeter Wave-induced Vibrational Modes in DNA as a Possible Alternation to Animal Test to Probe for Carcinogenic Mutations. Journal OF Applied Toxicology, VOL. 17(4), 1997: 243～246
[8] Timothy D. Dorney, William W. Symes, Richard G. Baraniuk AND Daniel M. Mittleman. Terahertz multistatic reflection imaging. J. Opt. Soc. Am. A, Vol. 19, No. 7, July 2002: 1432～1442.
[9] Jon L. Johnson, Timothy D. Dorney, and Daniel M. Mittleman. Interferometric Imaging With Terahertz Pulses. IEEE Journal ON Selected Topic IN Quantum Electronics VOL. 7, NO. 4, JULY/AUGUST
2001: 43～49
[10] Michael Schall and Peter Uhd Jepsen. Photoexcited GaAs surfaces studied by transient terahertz time-domain spectroscopy. January OPTICS LETTERS, Vol. 25, No. 1, January 2000: 13～15.
[11] E H Linfield, A G Davies, M B Johnston, A Dowd. Terahertz generation at semiconductor surfaces. Lasers for Science Facility Programme-Physics 2001/2002: 289～295
[12] J. V. Rudd, Quadrupole radiation from terahertz dipole antennas Anomalous optically generated THz beams from metal/GaAs interfaces. Optics Letters Vol. 25, No 20, October 2000: 1556～1558
[13] Nan M. Froberg, Bin Bin Hu, Xi-Cheng Zhang, and David H. Auston, Fellow. Terahertz Radiation from a Photoconducting Antenna Array. IEEE Journal of Quantum Electronics, Vol. 28, No. 10, October 1992: 443～448
[14] 吕振国、吴起、张希成．THz电磁场的新型电光探测技术及应用．物理，26(1)，1997：51～54
[15] Q. Wu and X.-C. Zhang. Ultrafast electro-optic field sensors. Appl. Phys. Lett., Vol. 68, No. 12, 18 March 1996: 1604～1606.
[16] 姜玉稀，程东方，赵冷柱，李娇．用电光晶体测量超快电磁辐射脉冲的几个问题．应用科学学报，20(3)，2002：291～295
[17] J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. U. Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof. Ultrafast local field dynamics in photoconductive THz antennas. Appl. Phys. Lett., Vol. 62, 1993: 1265～1267,
[18] J.T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse. Saturation properties of large-aperture photo-conducting antennas. IEEE J. Quantum Electron., vol. 28, 1992: 1607～1616
[19] J. V. Rudd. Quadrupole radiation from terahertz dipole antennas. Optics Letters, Vol. 25, No 20, October 2000: 1556～1558.
[20] Sang-Gyu Park, A. M. Weiner, Michael R. Melloch. High-Power Narrow-Band Terahertz Generation Using Large-Aperture Photoconductors. IEEE Journal OF Quantum Electronics., VOL. 35, NO. 8, August 1999:1257～1268
[21] A. S. Weling, B. B. HLI, N. M. Froberg, and D. H. Auston. Generation of tunable narrow-band THz radiation from large aperture photoconducting antennas. Appl. Phys. Lett., Vol. 64, No. 2, 10 January 1994:137～139
[22] 张民、吴振森、郭立新、印国泰．波导缝隙阵天线的电磁散射特性分析与校验．电子学报．，30(3)，2002．3：413～415。
[23] 周朝栋，王元坤，杨恩耀，天线与电波．西安：西安电子科技大学出版社 1994：152～178
[24] 施卫，梁振宪．高压超快GaAs光电导开关的耐压设计与绝缘保护．高电压技术．，24(1)，1998：12～16。
[25] 杨宏，王鹤，陈光德．多晶硅太阳电池的氮化硅钝化．半导体情报．，38(6)，2001：39～51。
[26] F.J. Zutavern, G.M. Loubriel, et. al. High power light activated semiconductor switches with sub-nanosecond rise times. IEEE MTT Symp. Rec., 1991: 377～380
[27] G.M. Loubriel, F.J.Zutavern, et. al. Measurement of the velocity of current filaments in optically triggered high gain GaAs switched. Appl. Phy. Lett.,Vol:64, No24,1994: 3323～3325.
[28] Hanmin Zhao, Jung H. Hur, et. al. lock-on effect in GaAs photocongductive switches. In Optical Activated Switching Ⅱ. SPIE Proc. Vol:1632, Los Angeles, CA, 1992: 274～280.
[29] F. J. Zutavern, G. M. Loubriel, M. W. O' Malley, W. D. Helgeson, and D. L. McLaughlin. High gain PCSS' s. in proc. 8~(th) IEEE Power Conf. San Diego, CA, 1991: 23.
[30] 施卫、梁振宪、徐传骧．高倍增GaAs光电导开关的设计与研制．西安交通大学学报．，32(8) 1998：19～23
[31] 施卫、梁振宪．高倍增超快高压GaAs光电导开关触发瞬态特性分析．电子学报．，28(2)，2000：19～23
[32] SHIWei. Optically Activated Charge Domain Model for High-Gain GaAs Photoconductive Switches. Chinese Journal OF Semiconductors., Vol. 22, No. 12Dec. 2001: 1481～1485.
[33] 施卫，梁振宪，冯军．Monte Carlo方法在高倍增GaAs光电导开关模拟中的应用．西安交大学报．，32(5)，1998：1～3页
[34] 张晓霞，潘炜，罗斌，吕鸿昌，陈建国，用直接模拟法分析量子阱半导体激光器瞬态响应．光子学报．，29(7)，2000：651～653页
[35] 葛德彪，闫玉波．电磁波时域有限差分方法．西安：西安电子科技大学出版社，2002：1～5
[36] 张国华，袁乃昌，付云起．FDTD方法分析光子带隙微带结构．微波学报．，17(4)，2001：14～17
[37] Yee K S. Numerical solution of boundary value problems involving Maxwell equations in isotropic media,IEEEE Trans Propagat., May AP-14(3), 1966: 302～307
[2] Bradley Ferguson And Xi-Cheng ZHANG. Materials for Terahertz Science and Technology. Nature Materials Vol: 1, SEPTEMBER 2002: 26～33.
[3] 王少宏、许景周、汪力、张希成．THz技术的应用及展望．物理 30(10)，2001：612～615
[4] Joel E. Boyd, Ari Briskman, Christie M. Sayes, Daniel Mittleman, and Vicki Colvin. Terahertz Vibrational Modes of Inverse Micelles. J. Phys. Chem. B 2002, 106, 2002: 6346～6353
[5] Daniel M. Mittleman, Stefan Hunsche, Luc Boivin, and Martin C. Nuss. T-ray tomography. OPTICS LETTERS, Vol. 22, No. 12 June 15, 1997: 904～906
[6] R. H. Jacobsen, D. M. Mittleman, and M. C. Nuss. Chemical recognition of gases and gas mixtures with terahertz waves. OPTICS LETTERS, Vol. 21, No. 24, December 15, 1996: 2011～2013.
[7] D.L. Woolard, T. Koscica AND D.L.Rhodes, Millimeter Wave-induced Vibrational Modes in DNA as a Possible Alternation to Animal Test to Probe for Carcinogenic Mutations. Journal OF Applied Toxicology, VOL. 17(4), 1997: 243～246
[8] Timothy D. Dorney, William W. Symes, Richard G. Baraniuk AND Daniel M. Mittleman. Terahertz multistatic reflection imaging. J. Opt. Soc. Am. A, Vol. 19, No. 7, July 2002: 1432～1442.
[9] Jon L. Johnson, Timothy D. Dorney, and Daniel M. Mittleman. Interferometric Imaging With Terahertz Pulses. IEEE Journal ON Selected Topic IN Quantum Electronics VOL. 7, NO. 4, JULY/AUGUST
2001: 43～49
[10] Michael Schall and Peter Uhd Jepsen. Photoexcited GaAs surfaces studied by transient terahertz time-domain spectroscopy. January OPTICS LETTERS, Vol. 25, No. 1, January 2000: 13～15.
[11] E H Linfield, A G Davies, M B Johnston, A Dowd. Terahertz generation at semiconductor surfaces. Lasers for Science Facility Programme-Physics 2001/2002: 289～295
[12] J. V. Rudd, Quadrupole radiation from terahertz dipole antennas Anomalous optically generated THz beams from metal/GaAs interfaces. Optics Letters Vol. 25, No 20, October 2000: 1556～1558
[13] Nan M. Froberg, Bin Bin Hu, Xi-Cheng Zhang, and David H. Auston, Fellow. Terahertz Radiation from a Photoconducting Antenna Array. IEEE Journal of Quantum Electronics, Vol. 28, No. 10, October 1992: 443～448
[14] 吕振国、吴起、张希成．THz电磁场的新型电光探测技术及应用．物理，26(1)，1997：51～54
[15] Q. Wu and X.-C. Zhang. Ultrafast electro-optic field sensors. Appl. Phys. Lett., Vol. 68, No. 12, 18 March 1996: 1604～1606.
[16] 姜玉稀，程东方，赵冷柱，李娇．用电光晶体测量超快电磁辐射脉冲的几个问题．应用科学学报，20(3)，2002：291～295
[17] J. E. Pedersen, V. G. Lyssenko, J. M. Hvam, P. U. Jepsen, S. R. Keiding, C. B. Sorensen, and P. E. Lindelof. Ultrafast local field dynamics in photoconductive THz antennas. Appl. Phys. Lett., Vol. 62, 1993: 1265～1267,
[18] J.T. Darrow, X.-C. Zhang, D. H. Auston, and J. D. Morse. Saturation properties of large-aperture photo-conducting antennas. IEEE J. Quantum Electron., vol. 28, 1992: 1607～1616
[19] J. V. Rudd. Quadrupole radiation from terahertz dipole antennas. Optics Letters, Vol. 25, No 20, October 2000: 1556～1558.
[20] Sang-Gyu Park, A. M. Weiner, Michael R. Melloch. High-Power Narrow-Band Terahertz Generation Using Large-Aperture Photoconductors. IEEE Journal OF Quantum Electronics., VOL. 35, NO. 8, August 1999:1257～1268
[21] A. S. Weling, B. B. HLI, N. M. Froberg, and D. H. Auston. Generation of tunable narrow-band THz radiation from large aperture photoconducting antennas. Appl. Phys. Lett., Vol. 64, No. 2, 10 January 1994:137～139
[22] 张民、吴振森、郭立新、印国泰．波导缝隙阵天线的电磁散射特性分析与校验．电子学报．，30(3)，2002．3：413～415。
[23] 周朝栋，王元坤，杨恩耀，天线与电波．西安：西安电子科技大学出版社 1994：152～178
[24] 施卫，梁振宪．高压超快GaAs光电导开关的耐压设计与绝缘保护．高电压技术．，24(1)，1998：12～16。
[25] 杨宏，王鹤，陈光德．多晶硅太阳电池的氮化硅钝化．半导体情报．，38(6)，2001：39～51。
[26] F.J. Zutavern, G.M. Loubriel, et. al. High power light activated semiconductor switches with sub-nanosecond rise times. IEEE MTT Symp. Rec., 1991: 377～380
[27] G.M. Loubriel, F.J.Zutavern, et. al. Measurement of the velocity of current filaments in optically triggered high gain GaAs switched. Appl. Phy. Lett.,Vol:64, No24,1994: 3323～3325.
[28] Hanmin Zhao, Jung H. Hur, et. al. lock-on effect in GaAs photocongductive switches. In Optical Activated Switching Ⅱ. SPIE Proc. Vol:1632, Los Angeles, CA, 1992: 274～280.
[29] F. J. Zutavern, G. M. Loubriel, M. W. O' Malley, W. D. Helgeson, and D. L. McLaughlin. High gain PCSS' s. in proc. 8~(th) IEEE Power Conf. San Diego, CA, 1991: 23.
[30] 施卫、梁振宪、徐传骧．高倍增GaAs光电导开关的设计与研制．西安交通大学学报．，32(8) 1998：19～23
[31] 施卫、梁振宪．高倍增超快高压GaAs光电导开关触发瞬态特性分析．电子学报．，28(2)，2000：19～23
[32] SHIWei. Optically Activated Charge Domain Model for High-Gain GaAs Photoconductive Switches. Chinese Journal OF Semiconductors., Vol. 22, No. 12Dec. 2001: 1481～1485.
[33] 施卫，梁振宪，冯军．Monte Carlo方法在高倍增GaAs光电导开关模拟中的应用．西安交大学报．，32(5)，1998：1～3页
[34] 张晓霞，潘炜，罗斌，吕鸿昌，陈建国，用直接模拟法分析量子阱半导体激光器瞬态响应．光子学报．，29(7)，2000：651～653页
[35] 葛德彪，闫玉波．电磁波时域有限差分方法．西安：西安电子科技大学出版社，2002：1～5
[36] 张国华，袁乃昌，付云起．FDTD方法分析光子带隙微带结构．微波学报．，17(4)，2001：14～17
[37] Yee K S. Numerical solution of boundary value problems involving Maxwell equations in isotropic media,IEEEE Trans Propagat., May AP-14(3), 1966: 302～307