Effects of processing parameters on electroluminescence of rf magnetron sputter deposited ZnS:ErF3

Abstract

Zn S : Er F 3 alternating current thin film electroluminescent (ACTFEL) devices are fabricated by rf plasma magnetron sputtering. In a full factorial design-of-experiment study, increasing deposition temperature, duty cycle on the doped target, and sputter gas pressure all result in increases in the 1.55μm near infrared (NIR) electroluminescence (EL) irradiance at 20V above threshold (B20). An increase in the EL threshold voltage (Vth) upon increasing the duty cycle of the undoped target is also reported. Postdeposition annealing of ACTFEL devices at 425°C for 1h improves the NIR EL irradiance by decreasing the F concentrations in the ZnS:Er films. The origins of these effects are discussed in terms of negative ion resputtering, surface mobility of sputtered species, crystallinity, and the effects of atomic concentration on the EL and radiative relaxation processes. A maximum irradiance, B20, of 147μW∕cm2 is measured for the 1.55μm NIR EL peak from ZnS:Er ACTFEL devices produced using a deposition temperature of 150°C, a duty cycle of 75%, an argon sputtering gas pressure of 24mTorr, and postdeposition annealing at 425°C for 1h in nitrogen.