Really, Seriously?

How does the gate bias in a Tunnel Field Effect Transistor align the conduction band of the intrinsic region with the valence band of the P region?

 I understand that once aligned, the electrons can tunnel through the boundary, but I don't understand how the applied voltage at the gate "aligns" the two bands.

 An appropriate gate voltage will raise the energy of the valence band electrons to an energy equal (or maybe just close to) the conduction band. At this point the semiconductor changes from insulator to conductor.

Voltage is a measure of the potential energy of electrons, IRCC.

Raise the voltage and your raise the PE of electrons in the vicinity.

 In this case, the potential energy of the intrinsic conduction band is lowered by increasing voltage, until it is down to the level of the p-type valence band, allowing for tunneling.

 One volt is defined as "the potential difference over which a positive coulomb of charge gains one Joule of potential energy".

So the direction of voltage is tied to the arbitrary definition of charge, in order to make it match up with the non-arbitrary definition of energy.