Electroluminescent and transport mechanisms of n-ZnO/p-Si heterojunctions

The distinct visible electroluminescence (EL) at room temperature has been realized based on n-ZnO/p-Si heterojunction. The EL peak energy coincided well with the deep-level photoluminescence of ZnO, suggesting that the EL emission was originated from the radiative recombination via deep-level defects in n-ZnO layers. The transport mechanisms of the diodes have been discussed with the characteristics of current-voltage (I-V) and light-output-voltage (L-V), in terms of the energy band diagram of ZnO/Si heterojunction. The tunneling mechanism via deep-level states was the main conduction process at low forward bias, while space-charge-limited current conduction dominated the carrier transport at higher bias. Light-output-current (L-I) characteristic of the diode followed a power law such as L similar to I-m, which showed a superlinear behavior at low injection current and became almost linear due to the saturation of nonradiative recombination centers at high current level. (c) 2006 American Institute of Physics.