Currently, optoelectronic integration (OEI) has been new trend and hot topic in the fields of optoelectronics technology and information engineering. Especially, light source integration and technology compatibility have hindered the development and application of OEI. In this work, a simple structure of electrically-pumped excitonic laser diode was rationally designed and fabricated, which could be directly integrated on Si substrate. An Au/MgO/ZnO metal-insulator-semiconductor(MIS) heterojunction device was constructed based on the island-like polycrystalline ZnO film. Ascribed to the large natural lattice mismatch between Si wafer and ZnO epitaxy layer, the heteroepitaxy growth induced highly-disordered polycrystalline island-like nanostructure on the surface of ZnO film. Thence, the active region (nearby ZnO/MgO heterojunction interface) yielded a strong scatter media due to the spatial variation of refractive index. It greatly enhanced optical scattering and favored a low-threshold random lasing. The simple device structure design and fabrication technology provide a feasible way towards the bottom-up ZnO based optoelectronic integration.