Enhanced blue emission from Si/Al2O3/Zn/ZnO multilayer films

• Effect of Al2O3 and Zn interlayer on PL properties of ZnO films is investigated.
• Zn buffer layer and thick Al2O3 interlayer induces remarkable PL enhancement.
• A model is proposed to interpret the change of the PL spectra.
• We propose that thick Al2O3 interlayer prevent charge carrier transfer between Si and Zn.
• More charge carrier recombination takes place on the ZnO layer and thus increase PL emission efficiency.

Si/Al2O3/Zn/ZnO multilayer films are prepared by magnetron sputtering. The conjunct effect of Al2O3 insulator interlayer and Zn buffer layer on the photoluminescence (PL) properties of ZnO films are investigated in detail. PL spectrum of Si/Zn/ZnO multilayer film (0 min) shows an evident violet peak and weak blue-green emission. As the deposition time of Al2O3 insulator interlayer is increased to 5 min, the violet peak disappears and there occurs both new peaks at 421 and 433 nm, respectively. Interestingly, as the deposition time of Al2O3 insulator interlayer is further increased to 15 min, a strong violet peak at 413 nm is observed. Also, all the peak intensity attain maximum. A model considering Ohmic contact formed between Zn and ZnO and Al2O3 insulator interlayer effect is proposed to interpret the change of the PL spectra.