漏电流问题限制了传统半绝缘氮化镓光电导开关的高压应用。提出在半绝缘GaN∶Fe衬底(激光触发区)上增加n型外延层并在其中构造垂直双扩散场效应晶体管元胞阵列(电触发区),即在传统纵向光电导开关结构上引入了一个由栅压控制的反向pn结,利用空间电荷区对载流子的耗尽作用降低半绝缘材料的漏电流。器件建模仿真显示,电、光触发区能合理分担10 kV外加偏置电压,在相同的电场偏置强度下,器件的漏电流低于传统光电导开关两个数量级,而且在绝缘栅开通过程中电触发区偏压能快速转移到光触发区,使光触发区在更高的动态偏置电场下被激光脉冲触发,提高了激光能量利用率。此外,计算分析了激光参数与器件输出特性之间的关系,以进一步提高激光利用率。

The problem of leakage current limits the application of traditional semi-insulated gallium nitride (GaN) photoconductive semiconductor switches (PCSSs) in high-voltage applications. Therefore, a n-type epitaxial layer is grown on the semi-insulated GaN∶Fe substrate (as a laser-triggered region), in which a cell array of vertical double-diffusion-field-effect transistors (as a voltage-triggered region) is constructed. In other words, a reverse pn junction controlled by the gate voltage is introduced into the traditional vertical PCSS structure for restraining the leakage current of the semi-insulated GaN due to the carrier depletion effect of the pn-junction space-charge region. The device simulation results show that the 10-kV bias voltage is reasonably shared by the laser- and voltage-triggered regions and the leakage current of the device is two orders of magnitude less than that of the traditional PCSS with the same bias electric field. Moreover, the results show that the bias voltage of the voltage-triggered region can be transferred to the laser-triggered region quickly with the gate opening; thus, the laser energy efficiency is heightened because the dynamic bias electric field increment across the laser-triggered region brings a high photocurrent peak. Moreover, the relationships between the laser parameters and the device output characteristics are calculated and analyzed to ensure high laser energy efficiency.