【作者】 屈光辉；

【导师】 施卫；

【作者基本信息】 西安理工大学 ， 微电子学与固体电子学， 2004， 硕士

【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。更多还原

【Abstract】 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, space-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.更多还原