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

Abstract

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 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 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. Index Terms-Channel waveguides, electroluminescent devices, flat-panel displays, gallium nitride, molecular beam epitaxy, optical telecommunications, rare earths. GaN thin-film growth by CVD and MBE, focused ion beam fabrication of photonic components and circuits, rare-earth-doped luminescent devices for flat-panel displays, and communications. He has authored over 290 published articles and over 300 conference and seminar presentations.766

Ultraviolet photoluminescence from Gd-implanted AlN epilayers

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] In particular, the large band gaps of GaN, AlN, and their alloys allow emission of higher energy rare earth transitions that are otherwise absorbed in smaller band gap host materials. Therefore, these materials may have application in visible displays or in white light systems that employ color-combining techniques.…”

Spectral and time-resolved photoluminescence studies of Eu-doped GaN

“…This broad excitation band overlaps higher lying intra-4 f Eu 3ϩ energy levels, providing an efficient pathway for carrier-mediated excitation of Eu 3ϩ ions in The visible and infrared light emissions from rare-earthdoped GaN ͑GaN:RE͒ are of significant current interest for applications in thin-film electroluminescence ͑EL͒ devices. [1][2][3][4] For achieving red light emission, the 5 D 0 → 7 F 2 intra-4 f transition of trivalent Eu 3ϩ ions seems most promising. Intense red photoluminescence ͑PL͒ around 622 nm from GaN:Eu ͑as-grown and ion-implanted͒ has been reported from several research groups.…”

“…[1][2][3][4][5][6][7][8][9] In addition, several EL device structures based on GaN:Eu have been demonstrated. [1][2][3][4][5] The optimization of present EL devices, however, requires a more detailed understanding of the incorporation, excitation, and emission properties of Eu 3ϩ ions in the GaN host matrix.Several studies have recently appeared focusing on the preparation and optical properties of GaN:Eu. 4 -11 Based on the comparison to RE ions in other III-V semiconductors ͑e.g., InP:Yb, 12 GaAs:Er 13 ͒, the most probable lattice location for Eu 3ϩ ions in GaN are ͑substitutional͒ Ga sites, which have C 3V symmetry.…”

“…[1][2][3][4] For achieving red light emission, the 5 D 0 → 7 F 2 intra-4 f transition of trivalent Eu 3ϩ ions seems most promising. Intense red photoluminescence ͑PL͒ around 622 nm from GaN:Eu ͑as-grown and ion-implanted͒ has been reported from several research groups.…”

Photoluminescence properties of in situ Tm-doped AlxGa1−xN

“…[1][2][3][4] Previous work on visible emission from RE-doped III-Ns was mainly focused on RE-doped GaN. [1][2][3] Photoluminescence ͑PL͒ and cathodoluminescence ͑CL͒ data have been reported from nearly all lanthanide ions doped into GaN.…”