Effects of buried oxide layer on working speed of SiGe heterojunction photo-transistor*

Abstract

The effects of buried oxide (BOX) layer on the capacitance of SiGe heterojunction photo-transistor (HPT), including the collector–substrate capacitance, the base–collector capacitance, and the base–emitter capacitance, are studied by using a silicon-on-insulator (SOI) substrate as compared with the devices on native Si substrates. By introducing the BOX layer into Si-based SiGe HPT, the maximum photo-characteristic frequency f t,opt of SOI-based SiGe HPT reaches up to 24.51 GHz, which is 1.5 times higher than the value obtained from Si-based SiGe HPT. In addition, the maximum optical cut-off frequency f β,opt, namely its 3-dB bandwidth, reaches up to 1.13 GHz, improved by 1.18 times. However, with the increase of optical power or collector current, this improvement on the frequency characteristic from BOX layer becomes less dominant as confirmed by reducing the 3-dB bandwidth of SOI-based SiGe HPT which approaches to the 3-dB bandwidth of Si-based SiGe HPT at higher injection conditions.

Surface modulation of halide perovskite films for efficient and stable solar cells

“…In addition to morphology and components, the interface is also critical to the photovoltaic performance of PSCs, as has been demonstrated in efficient silicon solar cells and other semiconductor devices with various interface structures. [30][31][32] Due to the imperfection of crystals at the interfaces, defects are formed and bring nonradiative recombination, leading to efficiency loss. Moreover, interface is the initial entrance for water to degrade the perovskite lattice.…”