Dong-seon Lee

Rare-earth-doped GaN: growth, properties, and fabrication of electroluminescent devices

A review is presented of the fabrication, operation, and applications of rare-earth-doped GaN electroluminescent devices (ELDs). GaN:RE ELDs emit light due to impact excitation of the rare earth (RE) ions by hot carriers followed by radiative RE relaxation. By appropriately choosing the RE dopant, narrow linewidth emission can be obtained at selected wavelengths from the ultraviolet to the infrared. The deposition of GaN:RE layers is carried out by solid-source molecular beam epitaxy, and a plasma N/sub 2/ source. Growth mechanisms and optimization of the GaN layers for RE emission are discussed based on RE concentration, growth temperature, and V/III ratio. The fabrication processes and electrical models for both dc- and ac-biased devices are discussed, along with techniques for multicolor integration. Visible emission at red, green, and blue wavelengths from GaN doped with Eu, Er, and Tm has led to the development of flat-panel display (FPD) devices. The brightness characteristics of thick dielectric EL (TDEL) display devices are reviewed as a function of bias, frequency, and time. High contrast TDEL devices using a black dielectric are presented. The fabrication and operation of FPD prototypes are described. Infrared emission at 1.5 /spl mu/m from GaN:Er ELDs has been applied to optical telecommunications devices. The fabrication of GaN channel waveguides by inductively coupled plasma etching is also reviewed, along with waveguide optical characterization.

Thermal Quenching of Photoluminescence from Er-Doped GaN Thin Films

Abstract The green (537 and 558 nm) and near infrared (1.54 μm) photoluminescence (PL) spectra of Er-doped GaN thin films have been investigated as a function of temperature, excitation wavelength, and pump intensity. Thermal quenching measurements showed that the integrated green Er 3+ PL intensity ( 4 S 3/2 / 2 H 11/2 → 4 I 15/2 ) remained nearly constant up to 150 K, but decreased at higher temperatures due to a less efficient Er 3+ excitation. The integrated infrared Er 3+ PL intensity ( 4 I 13/2 → 4 I 15/2 ) was found to be temperature-independent up to 250 K, but decreased slightly at higher temperatures due to the onset of non-radiative decay. Pump intensity PL studies revealed that the above-gap excitation cross-section is more than two orders of magnitude greater than the below-gap excitation cross-section. Within a simplified three-level model, the above-gap excitation cross-section was estimated to be ∼10 −16 cm 2 . This result indicates that Er 3+ ions can be excited efficiently through carrier-mediated processes in a forward-biased GaN:Er light emitting device.