An MOS capacitor is a main building block of an MOS Field Effect Transistor (MOSFET). In the last chapters we saw how charges accumulate in a MOS capacitor ignoring minority carriers inside the semiconductor. However, minority carriers play an important role especially when the applied voltage is relatively large. In this chapter we look at the operation of an MOS capacitor accounting for both minority and majority carriers.
Let’s consider a p-doped semiconductor. Apply a negative voltage and see what happens. Is this consistent with what you saw before?
Next apply a small positive voltage and observe what happens. Increase the voltage and wait a bit to let the system reaches a steady state. Repeat this until you reach the maximum voltage. Can you explain what happens by just considering generation and recombination rate at different points in space? Can you explain what you observe by looking at the band-diagram?
Change the doping concentration and repeat the experiments. What changes do you observe?
Donor Density (per cm3):
Applied Voltage (V)
What happens if we change the doping type? Repeat the experiments and see what changes.
Donor Density (per cm3):
Applied Voltage (V)