A 2-D bipolar junction transistor model for flexible inorganic semiconductors

In the deformed state, semiconductor devices typically undergo changes in electrical performance. The drift of collector current (Ic) in vertical bipolar junction transistors (BJTs) under uniaxial stress has been widely observed. The conventional electro-mechanical model of vertical BJTs explains this phenomenon through the piezojunction effect. However, due to the differences in the patterns of base and emitter, the morphology of vertical BJTs on the two-dimensional plane of the chip becomes increasingly complex. Due to the natural orthogonal anisotropy of monocrystalline silicon, variations in crystallographic orientation-dependent stress configurations within the chip plane result in differences in mechanical and electrical changes of the flexible inorganic semiconductors. To characterize this phenomenon, a model that combines bending orientations and Ic variation for ultra-thin BJTs is proposed. Experimental data demonstrate that this model effectively describes current gain of vertical BJTs under different bending orientations. This study introduces, for the first time, electro-mechanical anisotropy analysis for vertical BJTs under different crystallographic orientation-dependent stress configurations and utilizes a simple compact-effect model to describe this phenomenon. The model provides a theoretical foundation for electro-mechanical simulations of flexible BJTs.