Abstract
In order to improve the electrical and frequency characteristics of SiGe heterojunction bipolar transistors (HBTs), a novel structure of SOI SiGe heterojunction bipolar transistor is designed in this work. Compared with traditional SOI SiGe HBT, the proposed device structure has smaller window widths of emitter and collector areas. Under the act of additional uniaxial stress induced by Si0.85Ge0.15, all the collector region, base region and emitter region are strained, which is beneficial to improve the performance of SiGe HBTs. Employing the SILVACOⓇ TCAD tools, the numerical simulation results show that the maximum current gain βmax, the Earley voltage VA are achieved for 1062 and 186 V, respectively, the product of β and VA, i.e., β ×VA, is 1.975 × 105 V and, the peak cutoff frequency fT is 419 GHz when the Ge component in the base has configured to be a trapezoidal distribution. The proposed SOI SiGe HBT architecture has a 52.9% improvement in cutoff frequency fT compared to the conventional SOI SiGe HBTs.
Highlights
There has been increased interest in SiGe heterojunction bipolar transistors (HBTs) technology for microwave RF circuits because of its high-frequency and compatibility with silicon technology [1]
In order to improve the electrical and frequency characteristics of SiGe heterojunction bipolar transistors (HBTs), a novel structure of SOI SiGe heterojunction bipolar transistor is designed in this work
Under the act of additional uniaxial stress induced by Si0.85Ge0.15, all the collector region, base region and emitter region are strained, which is beneficial to improve the performance of SiGe HBTs
Summary
There has been increased interest in SiGe HBT technology for microwave RF circuits because of its high-frequency and compatibility with silicon technology [1]. A SiGe HBT device structure with a virtual substrate was proposed in ref. The improvement of frequency characteristics is limited, and the self-heating effect of the substrate is significant. The introduction of strain engineering can reduce the transit time of carriers in the collector, and effectively improve the frequency characteristics of the device. The proposed device improves the frequency characteristics by introducing stress, and uses SOI substrate structure with buried oxygen layer is used to reduce the self-heating effect brought by virtual substrate. The SOI technology and strain silicon technology are combined to introduce uniaxial stress into the SOI collector with N+ buried layer to form a new SOI SiGe HBT device structure. The structure has been proved to be able to achieve breakthroughs in the key frequency characteristics, i.e. fT > 400 GHz
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