【作者】 田立强；

【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】 半绝缘GaAs光电导开关(Photoconductive Semiconductor Switches简称PCSS’s)具有兼备宽频带和高功率容量特性，使其在超高速电子学和大功率脉冲产生与整形技术领域(大功率亚纳秒脉冲源、超宽带射频发生器等)具有广泛应用前景。特别是在一定的触发光能和偏置电场阈值下，光电导开关存在的非线性工作模式(或Lock-on效应)，使得PCSS’s在高压超快功率脉冲系统中的应用更为有效、方便、灵活。然而到目前为止，还没有一个令人满意的理论，对光电导开关的非线性工作模式进行全面的解释。此外，PCSS’s在工作中存在的击穿和可靠性问题，也是迫切需要解决的实际问题。 本文在通过对转移电子器件偶极畴的动力学特征作了深入分析的基础上，结合非线性PCSS’s的稳定性实验，对非线性PCSS’s的光激发电荷畴理论模型作了进一步的完善。指出非线性波形周期性的减幅振荡，是由于光电导开关所处电路自激振荡形成的交流场对偶极畴的阈值电场E_T和维持电场E_s进行控制，从而形成转移电子振荡器的两种主要工作模式：延迟偶极畴模式和猝灭偶极畴模式。非线性光电导开关的时间延迟效应则是由于半绝缘GaAs材料中的EL2深能级中心动态地改变开关中的电场、载流子浓度引起的；延迟时间的长短主要由满足成畴所需条件的时间决定。论文指出PCSS’s非线性工作模式是一种由光触发引起西安理工大学硕士学位论文的典型的畴现象。 通过对非线性PCSS’S载流子输运机制的深入研究，结合开关的击穿和寿命实验，对PCSS’S击穿机制及性能退化机理在理论上作了分析。指出电子俘获击穿机制与热击穿是开关击穿的主要原因。电子俘获击穿机制是导致热击穿的主要原因，而热击穿是导致开关彻底失效的根本因素。其主要作用机制为:偏置电场和陷阱电荷电场可产生大量热电子，热电子的数量和动能决定Ga一AS键的损坏程度，Ga一As的断裂程度反映PCSS’S的击穿类型，而退陷电荷的数量则反映了Pcss，S可恢复损伤的程度。开关退化的主要原因是:开关体内的丝状电流对开关芯片的损伤;以及电荷畴到达阳极时来不及放电而产生的电荷拥挤现象对开关电极接触表面的损坏。在此基础上提出了研制大功率长寿命PCSS’s的方法.更多还原

【Abstract】 Duo to the intrinsic characteristics of the GaAs material, Serai-insulating (SI) GaAs Photoconductive Semiconductor Switches (PCSS’ s) have more obvious advantages in the performance of both high power and ultra-fast switching than those PCSS’ s made of other materials and then can be widely used in ultrahigh speed electronics, field of high power microwave generation and pulse forming (pulse sources of high power ultra-fast electromagnetism,ultra-wide-band microwave generator). Especially the GaAs PCSS can take on particular phenomena of nonlinear characteristics (also known as lock-on effect or high-gain mode) witch made it be very availability., convenience and f lexibleness. Although the great importance was attached to the device research and application of GaAs PCSS, up to the present, there are no reliable theories that can correctly account for the observed transient characteristics produced by the nonlinear mode. In addition, the breakdown and the degeneration of PCSS’ s are serious problems in the applications.In this dissertation the mode of luminous charge domain is perfected ulteriorly by deeply studying the dynamics characteristic of high-fielddomain of the trans-electron device with experiment stability of nonlinear PCSS. First, we think periodicity and weakening surge of the nonlinear waveform is caused by self-excitation of the circuit. The electric field thresholds (Et) and maintenance field (Es) of lock-on are modulated by the AC electric field; the nonlinear waveform became two main modes of trans-electron oscillator, namely delay polar domain mode and quenched dipole domain mode. Second, it is found that the deep energy level play a important role in lock on and time delay. They can dynamically change the distribution of electric field, carriers and current densities in PCSS, caused output current to delay and also strengthen the local electric field enough to satisfy qualification of domain, and then cause avalanche. The time of delay is determined by the time of attaining the qualification of domain. Accordingly the mode of luminous charge domain is a preferable mode to explain the mechanism of nonlinear PCSS.On the basis of experiments of breakdown and reliability of PCSS, the mechanism of carriers propagating is deeply studied, and the breakdown characteristics and degeneration mechanism are analyzed in the theory. Firstly it is shown that the thermal breakdown and electron-trapping breakdown theories are the main reason causing the breakdown of PCSS. The electron-trapping breakdown is the main reason accelerating the thermal breakdown, and the thermal breakdown is the fundamentality factor of the breakdown of PCSS. The main points include: the bias electric field and the charges in the traps are the main reasons to generating hot electrons, the number and the kinetic energy of hot electrons are determinative for damage degree of Ga桝s bands, relaxation degree of Ga桝s network reflects the degree of breakdown, and the number of the detrapping of trapped electrons reflects the degree of restoration. Secondly the major mechanisms ofdegeneration of PCSS are caused by both the filamentary nature of the current in high-gain PCSS damage to the chip of the switch and the charge domain reached the anticathode causes the erosion of metal interface. Finally on this base a novel method is presented for longevity improvement of nonlinear PCSS.更多还原