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
Articles you may be interested in Study of correlation effects in an exactly solvable model twoelectron systemBecause they form the beginning of an isoelectronic series possessing electrons with antiparallel spins, H-, He, and Li+ lend themselves well to a study of electron correlation. The study is of three wavefunctions. Two introduce correlation: one by configuration interaction, the other by including Hylleraas-type correlation factors. For comparison, the third function is based on the Hartree-Fock approach. The correlation within the wavefunctions is demonstrated by presenting two-particle density difference maps, IlD(Tt; r2), relative to the uncorrelated approach, and graphs of the radial density D(r). Amongst the quantities calculated from the different treatments are (COS'Y12), where 'Y12 is the angle subtended by the electrons at the nucleus, (fl' f2), the coherent x-ray scattering contribution foo(X), and (rn), where -2~n~4. Results are compared throughout with those from a more accurate wavefunction. In addition, it was possible to study the effects of radial and angular correlation separately by producing the natural expansion for one of the correlated functions. The main conclusion is that as Z increases, angular correlation replaces radial correlation in being more important. Further, s-type correlation terms in the wavefunction cause the density to spread, whereas angular terms generally contract it. All such correlation effects tend to decrease with
This article focuses on the social interactions of several boys aged 3-5 years in the block area of a preschool classroom in a childcare setting. Using transcripts of video segments showing these boys engaged in daily play and interactions, the article analyses two episodes that occurred in the first weeks of the school year. At first glance, both episodes appear chaotic, with little appearance of order among the players. A closer analysis reveals a finely organized play taking place, with older boys teaching important lessons to the newcomers about how to be masculine in the block area. These episodes illustrate that masculinity is not a fixed character trait, but is determined through practice and participation in the activities of masculinity. Play and conflict are the avenues through which this occurs.
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