Rectification, Photoconductivity, and Photovoltaic Effect in Semiconducting Diamond

Studies of the rectification between a metal point and $p$-type semiconducting diamond show that the formation of the potential barrier is essentially independent of the work function of the metal. The rectifying barrier apparently is formed by the establishment of equilibrium between charges in surface and interior states as proposed by Bardeen for the case of silicon. The semiconducting diamonds are photoconducting in the ultraviolet and visible regions with the maxima occurring at 224, 228, 640, and 890 mμ. Generally, diamonds have not been observed to be photoconducting in the visible region; however, it has been observed that in some cases an enhancement of conductivity induced by ultraviolet radiation results upon simultaneous irradiation with red light. There is agreement between the spectral response of photoconductivity and photovoltages developed at metal contacts with the exception that photovoltages developed near 440 mμ were not obtained in photoconductivity.