Effective method for the determination of semiconductor band gap is the measurements of the photodiffusion current spectra (see : J. Phys. : Condens. Matter, V.18, 5323 (2006)). This method allows to determine both the band gap energy and the energy of different defects in semiconductor. In this case, unlike photoconductivity, the measurements are made without an applied electric field. And so there is no bending of the energy bands. Usually we used both optical and photodiffusion current measurements. If you need to test of band gap of unknown semiconductor we must first all to carry out the measurements of absorption spectra. In this case you get approximate value of bandgap. Then, it is necessary to perform the photoluminescence and reflection as well as photodiffusion current measurementd described above.

Attached articles also can be useful.

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