Mechanism and characteristic analysis and optimization of SiGeC heterojunction bipolar transistor with super junction

Abstract

A novel SiGeC heterojunction bipolar transistor (HTB) with super junction is presented. The effects of SiGeC base and super junction on device performance are analyzed in detail, and current transport mechanism of novel device is studied. Based on SiGeC/Si heterojunction technology, the high frequency characteristic of the novel device can be excellent. The breakdown voltage of device is improved greatly, because of two-dimensional direction of the electric field distribution in the collector region. The results show that the breakdown voltage of SiGeC HBT with super junction is increased by 48.8%, compared with that without super junction. More importantly, the introduction of super junction changes neither the high current gain nor the high frequency characteristics of SiGeC HBT. Compared with the Si bipolar transistor (BJT) with the same parameters, the novel device has a current gain that increases 10.7 times, and its cutoff frequency and maximum oscillation frequency are also improved greatly. A good trade-off is achieved among high current gain, high frequency and high breakdown voltage, in the novel SiGeC HBT with super junction. The layers and width of column region are designed to be optimal. With the increase in the number of column region layers, the breakdown voltage of the novel device is increased significantly, the current gain is improved somewhat, and the cutoff frequency and maximum oscillation frequency are reduced slightly. Taken together, the pnpn four-layer structure of super junction region is reasonable.