Erbium-doped GaN epilayers synthesized by metal-organic chemical vapor deposition
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0955-I10-05
Erbium-doped GaN epilayers synthesized by metal-organic chemical vapor deposition C. Ugolini1, N. Nepal1, J. Y. Lin1, H. X. Jiang1, and J. M. Zavada2 1 Department of Physics, Kansas State University, Manhattan, KS, 66506 2 U.S. Army Research Office, Durham, NC, 27709
ABSTRACT GaN is an excellent host for Er due to the low thermal quenching of radiative intra-4f Er3+ transitions at 1.54 µm. Thus, Er doped GaN structures are promising for emitters and amplifiers operating at the main telecommunication wavelength of 1.54 µm. We report on the experimental study and synthesis of Er doped GaN by metal organic chemical vapor deposition (MOCVD). Photoluminescence (PL) with above and below bandgap excitation energies were employed to study the optical properties of Er doped GaN. PL spectra of these Er doped layers exhibit a strong 1.54 µm emission, corresponding to the intra-4f transition of the 4I13/2 (first excited state) to the 4I15.2 (ground state) of Er3+. Secondary ion mass spectroscopy (SIMS) and xray diffraction (XRD) of the Er doped GaN shows the films to be of high crystalline quality with a high Er concentration (2-3 x 1021 cm-3) and low impurity concentrations. The mechanisms of optical transitions involving different excitation energies, and potential applications of Er doped GaN structures in the communication wavelength are also discussed. INTRODUCTION Implementing rare-earth atoms into a semiconductor host has been widely investigated due to the potential applications of rare-earth doped materials as efficient optical amplifiers and light-emitters. The primary element employed for these studies has been Er [1-15,17], since one of its intra-4f transitions corresponds to a wavelength of 1.54 µm, which is the minimum loss in current silica fibers. The problem with Er3+ emission in many semiconductors is the low emission efficiency at room temperature. However, it has been well recognized that the thermal quenching of the Er3+ emission is decreased significantly in wide bandgap semiconductors (WBGS) [4]. Thus, GaN is an optimum host for Er since its optical bandgap is 3.4 eV. Successful incorporation of Er into GaN has been achieved by methods such as ionimplantation, hydride vapor phase epitaxy (HVPE), metal organic molecular beam epitaxy (MOMBE), and molecular beam epitaxy (MBE) [5-15,17]. There have been reports of Er incorporation, leading to devices, such as light emitting diodes (LEDs), that produce wavelengths ranging from the visible to infrared (IR) [6,11,14]. But all such devices either suffer from strong emission lines in the visible region and/or a low quantum efficiency at the IR wavelengths. But, Er-doped GaN obtained by in-situ incorporation via MOCVD has not been achieved; even though devices based upon MOCVD grown III-nitrides are among the highest quality [16]. We report on the in-situ incorporation of Er into GaN epilayers by MOCVD, and their optical properties [17].
EXPERIMENT Trimethylgallium was used for the Ga source, and blue NH3 was used as the N source. Due to patent rest
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