Effects of oxygen pressure on n-ZnO/p-Si heterojunctions fabricated using pulsed laser deposition

ZnO films were prepared on p-Si substrates using pulsed laser deposition (PLD) and n-ZnO/p-Si heterojunctions were fabricated at different oxygen partial pressures. The effects of oxygen pressures on crystallinity and surface morphology of ZnO films and the I–V characteristics of n-ZnO/p-Si heterojunctions were studied. It was found that the films grown in the oxygen pressure range from 10−5–10−2 Torr were all c-axis oriented. The surface morphologies were strongly dependent on the oxygen partial pressure. The current–voltage (I–V) characteristics of the heterojunctions could be classified into two categories depending on the oxygen pressure. At low pressure (10−5–10−4 Torr), the I–V curves were similar to those of common p–n junctions. As the oxygen pressure increased to 10−3 Torr, the I–V curves changed markedly. Based on the I–V characteristics, an energy band diagram of n-ZnO/p-Si was proposed.