You can explain the shift of Fermi level in n-tye and p-type dopants in this website:

http://www.physics-and-radio-electronics.com/electronic-devices-and-circuits/semiconductor/extrinsic-semiconductor/fermi-level-in-extrinsic-semiconductor.html

Theoretically, you can justify the shift by adjusting the concentration of dopants (n/p types). With the same t period but the different velocity and/or various conditions, the results should be different.

How do you measure the effect? Are you sure you are not creating a dopan film on top? Which are the conditions?

In general the laws that control conductivity are true in the low concentration regime. If yo see an abrupt change in the properties it means, in general, that you induce a phase (I-type) change.

You can explain the shift of Fermi level in n-tye and p-type dopants in this website:

http://www.physics-and-radio-electronics.com/electronic-devices-and-circuits/semiconductor/extrinsic-semiconductor/fermi-level-in-extrinsic-semiconductor.html

Theoretically, you can justify the shift by adjusting the concentration of dopants (n/p types). With the same t period but the different velocity and/or various conditions, the results should be different.

But that is just shifting of the Fermi level from the middle of the band gap with the doping. That is pretty well known phenomena for GaAs for example.

Dear Marina

Greetings

The change in the impurity concentration is the one which shift the maximum value of the valence band  and thus shift occurs these depend on the substrate temperature , the evaporation time ,the distance between the substrate  and  the   evaporation source , the mass of the vaporized material and the pressure chamber.  If the concentration of n-type are much different from the p type  we get a abrupt junction  type it occurs a shifting in the edge of the valence maximum band so you must install all the evaporated factors  and change one (the impurity concentration factor).The Fermi level also shifted follow the change in the impunity and the type of carriers. You can justified this by change the previous factors in addition to heat treatment after deposition processes.The energy gap will as well as change of a specific sample.

With best regards     

It depends on what your "band shift" measurement is. 

As Gia Quyet Ngo mentioned, the fermi level shifts with doping. If the fermi level shifts all the way out of the band gap, then measurements like light absorption will begin to change, as if the band gap itself were changing. That one is called Moss-Burnstein shift.