Photoreflectance studies of optical transitions in GaNPAs intermediate band solar cell absorbers

Photoreflectance spectroscopy is used to study optical properties of GaNPAs for the intermediate band (IB) solar cell absorbers. The IB is created in GaNPAs by the incorporation of ~2% of N atoms and the required partial occupation of the intermediate band with electrons is realized by doping with Si donors. Undoped and p-type doped (Be doped) GaNPAs films are studied as a references. Observation of all three absorption bands: VB → IB (a transition between the valence band and the IB), VB → CB (a transition between the valence band and the conduction band), and IB → CB (a transition between the IB and the conduction band), demonstrate that n-type doped GaNPAs layers act as intermediate band solar cell absorbers.