Experimental Comparison of Negative Capacitance Behaviour In Discrete Commonly Available Si Based Diode Connected MOSFETs and BJTs

In this work, the negative capacitance behaviour of commonly available discrete Si-based semiconductors (MOSFET and BJT) is presented. This was accomplished by conducting direct capacitance measurements of the two selected semiconductor devices at set biasing voltages and frequencies, where two of the three pins were shorted. Three distinct frequency values were used. A statistically significant number of semiconductor devices (thirty) from the same batch were measured. The results show that in 17 of the 24 tests conducted, negative capacitance behaviour was observed. For the chosen MOSFET, the maximum negative capacitance observed ranges from -530 pF to -1.99 mF. For the chosen BJT, the maximum negative capacitance observed ranges from -135 pF to -29 mF. A striking similarity in the capacitance-voltage mathematical model was observed for the graded doping profile mathematical model. This work shows that negative capacitance behaviour in discrete semiconductors does exist and should be considered when designing for frequency-sensitive applications, as it can have a large impact should inductive-based components be present. This work depicts one viable way of determining the negative capacitance a device exhibits through experimental measurements.