The Growth Of ZnO Films On Si By MOCVD And Electroluminescence From N-ZnO/MgO/p-Si Heterojunction Devices

As a wide direct bandgap semiconductor material, ZnO has a bandgapof3.37eV at room temperature with exciton binding energy of60meV,which determines its important applications on ultraviolet light-emittingdiodes and laser devices. However, the difficulty of preparation stableand reliable p-ZnO materials has been binding up the development ofZnO-based photoelectric devices. So constructing n-ZnO and other p-typesemiconductor materials to heterojunction devices has been anotherresearch focus. Due to its potential applications in the field ofoptoelectronic integration, ZnO/Si heterojunction has become animportant option for the people.This article first introduced a thin MgO buffer layer on Si substratesby magnetron sputtering technique to reduce the lattice mismatch of ZnOand Si. Then we grew ZnO thin films on MgO buffer layers by metalorganic chemical vapor deposition (MOCVD) technology. Finally the n-ZnO/MgO/p-Si heterojunction LEDs were fabricated. The experimentsmainly showed the effects of the buffer layer thickness and annealingtemperatures on the ZnO epitaxial growth and the luminescenceperformance of ZnO/MgO/p-Si heterojunction devices. Concrete researchcontents are as follows:1、The influence of buffer layer thickness on the ZnO films wasstudied. The research found that thinner MgO buffer layers can improvethe surface morphology and the optical quality ZnO thin films and canalso optimize the crystallization quality of the films. 2、The influence of annealing temperatures of MgO buffer layerson the ZnO films was studied. It’s found that buffer surface morphologychanged as the annealing temperature increased, which further influencedthe later epitaxial growth of ZnO. The size of the ZnO nanorods gotsignificantly change when annealing temperature was750℃. However,the crystallization quality of ZnO thin film became worse and stress in thefilm increased apparently.3、The luminescence performance of ZnO/MgO/p-Si heterojunctiondevices was studied and luminescence mechanism of the devices wasfurther analyzed through the band theory. The I-V tests showed theheterojunction devices had good rectifying characteristics. Theelectroluminescent (EL) spectra of devices covered from370nm to600nm in UV-visible region under forward bias, which was consistent withphotoluminescence (PL) spectra of ZnO.