Christopher C. Baker

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.

Optical amplification and electroluminescence at 1.54 μm in Er-doped zinc silicate germanate on silicon

Optical amplification and electroluminescence at 1.5 μm is reported in Er-doped Zn2Si0.5Ge0.5O4 (ZSG:Er) on silicon. ZSG:Er films were deposited by rf sputtering from a composite target in Ar/O2 mixtures. Channel waveguides were fabricated by plasma etching with Cl/Ar. The refractive index of ZSG:Er was found to be 1.75 at 1.54 μm. Signal enhancement greater than 13 dB and an internal gain of ∼2 dB have been achieved by optically pumping a 4.7 cm ZSG:Er amplifier. Electroluminescence at 1.5 μm was achieved using an ac device structure with a ZSG:Er central layer and upper and lower dielectric layers.

Photoluminescent and electroluminescent Zn/sub 2/Si/sub 0.5/Ge/sub 0.5/O/sub 4/:Mn thin films for integrated optic devices

The optical, photoluminescent (PL), and electroluminescent (EL) properties of Zn/sub 2/Si/sub 0.5/Ge/sub 0.5/O/sub 4/:Mn (ZSG:Mn) have been studied in order to determine its viability as a light source for integrated optics systems. ZSG:Mn thin films were deposited at room temperature by RF-sputtering on Si substrates. EL devices (ELDs) were fabricated using transparent indium-tin oxide electrodes. ELDs using as-deposited ZSG:Mn films emitted bright orange light with a broad spectrum at 590-660 nm. Annealing at 700/spl deg/C resulted in a color shift to green emission in a band from 510 to 550 nm and peaking at 520 nm. Ridge waveguides fabricated by induction-coupled plasma etching yielded an optical loss of 3.8 dB/cm at 633 nm. Prism coupling experiments revealed a decrease in the film refractive index as the result of the anneal. The combination of strong PL, EL, and low waveguide loss demonstrates the strong potential of transition metal- and/or rare-earth-doped ZSG as a robust light source for integrated optic systems.

Gain characteristics of Er-doped ZSG waveguide optical amplifiers

This paper studies the spectral characteristics of a ZSG (Zn/sub 2/Si/sub 0.5/Ge/sub 0.5/O/sub 4/) host doped with approximately 0.5 at.% Er and the absorption and emission cross-sections at 1.5 /spl mu/m determined using the Ladenburg-Fuchtbauer relationship. The population statistics of the Er atoms are estimated from a rate equation model and a measured spontaneous emission power vs. pump power curve, and the calculated absorption and emission cross sections and populations are used to calculate the gain of waveguide amplifiers. The calculated gain is in good agreement with the measured gain, confirming the potential of ZSG for integrated waveguide amplifiers and enabling quantitative waveguide amplifier design for other geometries or Er densities.

1.5 /spl mu/m Zn/sub 2/Si/sub 0.5/Ge/sub 0.5/O/sub 4/:Er electroluminescent waveguide amplifiers

In this paper, we report on Er-doped ZSG waveguide amplifiers and electroluminescent devices (ELDs). A 3.5 /spl mu/m wide ZSG:Er optical amplifier with a core thickness of 1.1 /spl mu/m and a length of 4.7 cm was fabricated. The refractive index variation with wavelength was obtained using a variable wavelength spectroscopic ellipsometer with a 0.27 /spl mu/m ZSG:Er sample. The results indicate that electroluminescent optical amplifiers in ZSG:Er films are possible.

Rare earth doped GaN electroluminescent devices

In this paper, we discuss the fabrication, operation and aplications of rare-earth-doped GaN electroluminescent devices (ELDs). GaN:RE ELDs. GaN:RE ELDs emit light due to impact excitation of the RE ions by hot carriers followed by radiative relaxation. By appropriately choosing the RE dopant, narrow line width emission can be obtained at selected wavelengths from the ultraviolet to the infrared. The deposition of GaN:RE layers is carried out primarily by MBE. GaN growth mechanism and optimization for RE emission are discussed based on RE concentration, growth temperature, and III-V ratio. We have investigated the optimum growth conditions of RE doped GaN phosphors.