Growth and Properties of Sn-Doped ZnO Nanowires for Heterojunction Diode Application

Well-crystalline Sn-doped ZnO nanowires were grown on p-type silicon substrates by simple non-catalytic thermal evaporation process. The prepared nanowires were examined in terms of their morphological, compositional and structural properties which revealed that the as-grown nanowires are well-crystalline Sn-doped ZnO, possessing wurtzite hexagonal phase structure and grown in very high density over whole silicon substrate. Further, the as-grown n-Sn-doped ZnO nanowires were used to fabricate n-Sn-ZnO/p-Si heterojunction diode. Temperature dependant electrical properties (294-353 K and 373-433 K) of the fabricated heterojunction diode were studied in the forward and reverse bias conditions and presented in this paper. The current-voltage characteristics at varying temperature of the heterojunction diode reveal that both the quality factor and Schottky barrier height depend on temperature. However, the mean barrier height is estimated similar to 1.2 eV in one attempt of analysis when a Gaussian distribution of low barrier heights is considered and found almost similar to 1 eV in another attempt when the Richardson plot is linearized. Furthermore, effective barrier heights of 0.55-0.75 eV are extracted in the temperature range 294-433 K when Tung model is used. These correspond to barrier heights of 0.93-0.35 eV extracted from C-V analysis in the same range of temperatures. Although the latter results from C-V analysis exhibit closer correlation with the Schottky barrier heights extracted from I-V analysis but the discrepancy between them still exist.