Region-dependent behavior of I–V characteristics in n-ZnO:Al/p-Si contacts

The discrepancy of rectifying characteristics in n-ZnO:Al/p-Si heterojunctions from diode to diode was demonstrated by region dependent dark I–V characteristics, where the junction is laterally cut to sequentially decrease the area. Further investigation shows that the junction (2.1×2.1 cm2) with the barrier height Φ=0.693 eV consists of one part (2.1×1.4 cm2) with Φ=0.695 eV and the other part (2.1×0.7 cm2) with Φ=0.686 eV. It is found that reverse currents saturate with different values of 3.6×10−3, 2.5×10−3 and 1.58×10−3 A for the light I–V curves of the three junctions with the same areas. To explain this peculiarity, the probable reason is discussed in terms of carrier transportation through the spatially fluctuating barrier.