Dear friend Lydia Lee

The Fermi level of an intrinsic semiconductor can be influenced by the substrate, but it is not permanently changed to p-type or n-type. The reason is that the Fermi level is a function of both the intrinsic carrier concentration and the extrinsic dopant concentration. When a semiconductor is in contact with a substrate, charge transfer occurs between the semiconductor and the substrate, and the Fermi level is adjusted to reach equilibrium between the two materials. This can result in a shift in the Fermi level relative to the intrinsic position.

However, this shift is temporary and the Fermi level will return to the intrinsic position once the semiconductor is removed from the substrate. The substrate does not change the intrinsic carrier concentration of the semiconductor, so it cannot permanently change the type of semiconductor.

References:

1. S. M. Sze and K. K. Ng, Physics of Semiconductor Devices, John Wiley & Sons, Inc., 2007.

2. C. Kittel, Introduction to Solid State Physics, John Wiley & Sons, Inc., 2005.