Some of the electrons have energy because heat is enough to cause bond from forming at the electron emitted cause the semiconductor. Electrical power when they are plugged in to this substance.
Some electron has enough energy to heat is lost up the vacancy caused by the bonding electrons come off, causing the semiconductor. Conductive when an electric field to connect with this material.
Some electron energy due to the heat, enough to let go of the bond created space up electrons off cause the semiconductor. Conductivity when there is an electric field to connect to this substance.