A silicon pn junction diode is characterized by a junction capacitance defined asWhere Ks...

A silicon pn junction diode is characterized by a junction capacitance defined as

Where Ks = 11.8 for silicon, ε0 is the vacuum permittivity, A = the cross- sectional area of the junction, and W is known as the depletion width of the junction. Width W depends not only on how the diode is fabricated, but also on the voltage applied to its two terminals. It can be computed using

Thus, diodes are frequently used in electronic circuits, since they can be thought of as voltage-controlled capacitors. Assuming parameter values of N = 1018 cm-3, Vbi = 0.57 V, and using q = 1.6 × 10-19 C, calculate the capacitance of a diode with cross-sectional area A = 1 μm × 1 μm at applied voltages of VA = –1, –5, and –10 volts.