Ultraviolet electroluminescence from ZnO/p-Si heterojunctions

Nominally undoped ZnO films were deposited by reactive sputtering on the lightly boron-doped (p(-)) and heavily boron-doped (p(+)) silicon substrates. The sputtered ZnO films were identified to be highly < 002 > oriented in crystallinity and n type in electrical conductivity. The current-voltage (I-V) characteristics revealed that the ZnO/p(-)-Si heterojunction exhibited well-defined rectifying behavior while the ZnO/p(+)-Si heterojunction did not possess rectifying function. As for the ZnO/p(+)-Si heterojunction, it was electroluminescent to a certain extent in the visible region under sufficient forward bias with the positive voltage on the silicon substrate, while it emitted ultraviolet light characteristics of near-band-edge emission of ZnO under the reverse bias, which significantly dominated the visible emission. In contrast to the ZnO/p(+)-Si heterojunction, the ZnO/p(-)-Si heterojunction did not exhibit detectable electroluminescence (EL) under either forward or reverse bias. The I-V characteristics and EL mechanism of the above-mentioned heterojunctions have been tentatively explained in terms of the energy-band structures of the heterojunctions. (c) 2007 American Institute of Physics.