Study On Zn₂SiO₄/Si Luminescent Thin Film And Device

The evolution from microelectronic integration to opto-electronic or optonic integration is required due to the development of information technology. Because of the state of arts of the silicon based IC technology, emphasis is focused on the silicon based opto-electronic integrated circuits (Si-OEIC). The key point of Si-OEIC is to develop silicon IC process compatible light emission devices on silicon wafer. Due to its high luminescent efficiency, high stability, changeable emission wavelength, and compatibility with silicon based IC process, zinc silicate doped with transition metal or rare earth elements, i.e. Zn₂SiO₄:M, is of great interest for the researchers in recent years. On the other hands, few systematic investigation on Zn₂SiO₄:M thin films on Si substrate has been reported.Zn₂SiO₄ and Zn₂SiO₄:.M thin films were prepared on SiO₂/Si substrate by high temperature annealing after spin coated with sol containing Zn. The properties of Mn doped Zn₂SiO₄ (Zn₂SiO₄:Mn) films and factors influencing the luminescent properties were studied. Luminescent Zn₂SiO₄:M thin films with other wavelengths were also prepared on Si substrate by doping with other rare earth elements. Finally, a silicon based electroluminescent prototype device using Zn₂SiO₄:Mn as light emission layer was prepared based on the idea of planar structured silicon based IC.The results in this dissertation indicate that doped zinc silicate (Zn₂SiO₄:M) luminescent thin films can be used in silicon based electroluminescent devices. Zn₂SiO₄:M thin films were stable in luminescence, and luminescence with different wavelength can be achieved by doping with different element. Furthermore, the preparation was compatible with the silicon based IC technique. It was reasonable for the potential usage in some silicon based opto-electronic devices of this luminescent film.The main results are as follows:1. Zn₂SiO₄ and ZnSiO:Mn thin films were prepared on Si substrate by solid-phase reaction of ZnO and SiO₂ and the factors influencing the characteristics of thin films were studied. It's observed that: 1) ZnO didn't transformed into Zn₂SiO₄ through reaction at temperature lower than 800℃; and 2) both ZnO and Zn₂SiO₄ existed in the films processed in the intermittent temperature range of 900-1000℃; 3) only Zn₂SiO₄ existed for process temperature higher than 1050℃. The relative amount of ZnO and Zn₂SiO₄ phases and the concentration of Mn²⁺ are main factors influencing the photoluminescence intensity of the films.2. Although Mn2+ substitutes Zn2+ in Zn2SiO4 and acts as luminescent center when Mn2+ concentration is lower than 10mol%, concentration quenching takes place and resulted in lower photoluminescence at Mn2+ concentration of 2mol%. acting as luminescent center. Z^SiO^Mn emit green light peaked at wavelength of 525nm with a decay time of about 21ms for Mn2+ concentration of 2mol%.3. It was founded that the existence of a proper amount of ZnO in the films was beneficial to enhance the luminescent intensity of the films. It's suggested that by intentionally controlling the reaction temperature and time duration, optimism photoluminescence intensity could be obtained. Experimental results showed that films annealed at 1050°C for 2 hours has the highest relative luminescent intensity.4. The phenomenon in point 3 was qualitatively explained using the "Quantum Confinement - Luminescence Center" (QCLC) model for the photoluminescence of porous silicon. The electrons and holes in ZnO tunneled into the energy level of Mn2+ through the ZnO-Zn2SiC?4 boundary and recombined through Mn2+.5. Films emitting light with different wavelengths (618nm, 370-430nm, and 545nm and 490nm) were obtained respectively by doping different rare earth elements (Eu, Ce, and Tb) into Zn2SiC>4 films. Concentration quenching took place at 2mol% of Eu, 1.25mol% of Ce, and 3.5mol% of Tb respectively for the luminescent thin films of Zn2Si04:Eu, Zn2Si04:Ce, and Zn2Si04:Tb.6. A planar structured electroluminescent prototype device was designed and fabricated using Zn2SiO4:Mn film as the luminescent layer. The device emitted green light (centered around 525nm, consistent with the PL spectrum) under an alternative field with frequency of 200Hz-lkHz and voltage of 40V-80V. The EL emission mechanism was explained using Accumulated Electric Field and Hot Electron Impact model.