AC Operation of GaN:Er Thin Film Electroluminescent Display Devices

Abstract

ABSTRACTThin-film electroluminescence has been obtained from GaN:Er deposited directly on amorphous dielectric layers. Electroluminescent device (ELD) structures consisting of a dielectric/GaN/dielectric were formed on p+-Si substrates. In contrast to previous GaN:Er ELDs which used epitaxial growth conditions on crystalline substrates and were operated under DC bias, these ELDs were operated under AC bias. A maximum luminance value of 300, 60, and 15 cd/m2 has been achieved from GaN:Er and AlGaN:Er AC-ELDs biased at 180 V and 100, 10, and 1 kHz, respectively. The emission spectra, which originate from Er3+ 4f-4f transitions, consist of dominant visible emission at ∼537/558 nm and infra-red (IR) emission at 1.5 μm. A violet emission peak at 415 nm indicates that hot carriers can gain up to ∼3 eV energy for an applied voltage corresponding to 1.5 MV/cm applied field. The emitted intensity initially increases linearly with frequency, followed by a trend towards saturation. The frequency for 3 dB reduction from the linear relation is at ∼65 kHz for visible emission and ∼8 kHz for infrared emission. The saturation trends can be explained in terms of the spontaneous emission lifetimes of the visible (∼10 μs) and IR (∼1ms) Er3+ emissions.