Pulsed KrF laser annealing of ZnS:Mn laterally emitting thin film electroluminescent displays

Pulsed KrF (248-nm) laser annealing was investigated as a post-deposition process for RF sputtered ZnS:Mn phosphor layers used in laterally emitting thin film electroluminescent (LETFEL) displays. LETFEL devices consist of a phosphor layer sandwiched between two insulating thin films (Y2O3), grown onto silicon substrates patterned with micro-mirrors (SiO2). The micro mirror structure permits surface viewing by reflecting laterally emitted light due to internal waveguiding effects. Laser irradiation of the uncoated phosphor layer was performed using KrF excimer 248-nm laser pulses of 20 ns under an argon overpressure of 10.34 bars to limit laser ablation. The influence of the laser irradiation fluence on the LETFEL performance was investigated from 0.3 to 1.5 J/cm2. In this paper, we have reported the brightness-voltage characteristics of laser annealed, non-annealed and thermally annealed devices at 500°C for 1 h. It is shown that the onset for light emission (threshold voltage) decreases with laser annealing. Using this novel method of annealing, the brightness of LETFEL devices is observed to increase with increasing laser fluence