Performance improvement of n-TiO2/p-Si heterojunction by forming of n-TiO2/polyphenylene/p-Si anisotype sandwich heterojunction

The n-TiO2/polyphenylene (PPh)/p-Si heterojunction devices were fabricated in which PPh film and TiO2 top layer were grown on p-Si substrates by diazonium modification method and cathodic electrodeposition, respectively. The XPS, UV-vis diffuse reflectance and STM analyses of the films were performed. After the characterization of deposited films and the fabrications of n-TiO2/PPh/p-Si sandwich devices, the electrical measurements of nine devices were carried out from the current-voltage (I-V) characteristics, at room temperature. The I-V characteristics of n-TiO2/PPh/p-Si heterojunctions were compared with TiO2/p-Si heterojunctions, one of them was analysed in more detailed and it was observed that the n-TiO2/PPh/p-Si gave better performance than TiO2/p-Si heterojunctions such that lower ideality factor, higher rectification ratio and more stable reverse current characteristics. Then, the main device parameters of n-TiO2/PPh/p-Si were compared with many devices reported in literature based on TiO2/p-Si device and TiO2 preparation techniques. Furthermore, the rectification ratio of n-TiO2/PPh/p-Si heterojunction was 9.42 x 10(5), while it was 5.80 x 10(2) for TiO2/p-Si heterojunction. Later, the capacitance-voltage (C-V) and conductance-voltage (G-V) measurements of the n-TiO2/PPh/p-Si heterojunction was performed depending on applied frequency and bias and it was observed that the values of capacitance and conductance were found a strongly function of bias voltage.