Switching rate and power capacity improvement of semiconductor power device by effect of magnetic fields

研究了磁场对功率半导体器件中载流子行为的影响，以获得设计脉冲功率应用中具有高di/dt特性的高电流密度开关器件所需的技术数据。采用波长为1.55μm的红外探测激光自由载流子吸收法测量了功率半导体器件基本结构pin二极管的载流子分布的时空变化。对探测光束进行了分析，获得了40μm的空间分辨率。成功地观察到了由洛伦兹力引起的载流子密度的空间非均匀性。讨论了磁场增加导通电阻的因素。载流子密度分布的空间不均匀性导致器件中电流的有效截面减小。作为实际使用的功率器件，作为脉冲功率技术中快速开关器件的可能候选者而备受关注的SI晶闸管被用来检查载流子行为。半导体功率器件中的载流子用于消除势垒并将电荷从阳极转移到阴极。对于快速脉冲开关，即使电流密度相当高，参与转移电荷的载流子的量也相对较小。在这项研究中，提高关断特性和建立高重复操作的SI晶闸管的可能性被证实。

The influence of magnetic fields on carrier behavior in power semiconductor devices was examined in order to obtain technical data required for designing devices that can switch in high-current density region with high di/dt characteristics for pulsed power applications. Free carrier absorption method using the infrared probe laser with wavelength of 1.55μm was employed to measure spatial and temporal change in carrier distribution of a pin-diode, which has a basic structure of power semiconductor devices. The probe laser beam ray was analyzed and spatial resolution of 40μm was obtained. Spatial nonuniformity of the carrier density caused by Lorentz force was successfully observed. The factor contributed to the increase of on-resistance by the magnetic field was discussed. The spatial nonuniformity of the carrier density distribution led to the decrease of the effective cross section of the current in the device. As actually utilized power device, a SI-thyristor, which attracted much attention as a possible candidate for a fast switching device in pulsed power technology, was adopted to examine the carrier behavior. The carrier in the semiconductor power devices works to remove the potential barrier and to transfer electric charges from the anode to the cathode. The amount of carrier involved in transferring the electric charge was comparatively small for the fast pulse switching, even if the current density was considerably high. In this research, the possibility of improving the turn-off characteristics and establishing high-repetition operation of the SI-thyristor was confirmed.