The knee voltage for germanium is approximately 0.3 V, not 0.2 V. The knee voltage, also known as the cut-in voltage, is the minimum forward voltage that must be applied to a semiconductor diode to allow significant current to flow through it.

In the case of germanium, the knee voltage is around 0.3 V because of its intrinsic properties. Germanium has a larger bandgap energy than silicon, meaning that more energy is required to excite electrons from the valence band to the conduction band. This results in a higher forward voltage drop across the diode before substantial current flow can occur.

The knee voltage is an important parameter in diode circuits, as it determines the threshold voltage at which the diode starts conducting. It is also a key factor in the design and operation of various semiconductor devices, such as transistors, rectifiers, and solar cells.