Wide-gap semiconductors are often unipolar and can form type II bipolar heterostructures with large band discontinuities. We present such diodes with very high rectification larger than 1 × 10(10). The current is assumed to be entirely due to interface recombination. We derive the ideality factor for both symmetric and asymmetric diodes and find it close to 2 in agreement with experimental data from NiO/ZnO and CuI/ZnO type II diodes. The comparison with experimental results shows that the actual interface recombination rate is orders of magnitude smaller than its possible maximum value.
Keywords: diode; heterostructure; ideality factor; interface recombination; trap; type II band lineup.