Concentration of charge carriers is usually measured via Hall effect

Actually, I would like to study the semiconductor surface properties such as separation and recombination and transport of photoinduced charge carriers under illumination

well, in this case you can take Hall measurements as function of illumination (dark/bright) and contact size/position to separate bulk and surface effects.

Sir,

You can try Mott−Schottky measurements using a Galvanstat/Potentiostat instrument

for details, you can find elsewhere

 I agree with Thomas Walther, the use of Hall experiment is very useful

By Hall effect you can determine the. Concentration of e- and h+

I have same articles in this filed