Opto-electronic properties of p- and n-type delafossite, CuFeO2

CuFeO2, doped with Mg, is a p-type semiconductor with a hole mobility of 10−5 m2Vs; the electron mobility in n-type CuFeO2, doped with Sn, is 10−10 m2Vs. From photo-electrochemical measurements the valence band edge is found to be 4.9 eV below the vacuum level. The valence band is made up of mainly Cu-3d wave functions; a deeper lying O-2p band has its edge at 7.1 eV. The indirect allowed bandgap is 1.15 eV; further optical transitions occur at 2.03 and 3.35 eV. The results are compared with similar data for the delafossites CuMO2 with M = Al, Cr, Ga and Y.