Abstract
Erbium doped GaN (Er:GaN) is a promising candidate as a novel gain medium for solid-state high energy lasers (HELs) due to its superior physical properties over a synthetic garnet such as Nd:YAG. Er:GaN emits in the 1.5 µm region, which is retina-safe and has a high transmission in the air. We report photoluminescence (PL) studies performed on Er:GaN epilayers synthesized by the hydride vapor phase epitaxy (HVPE) technique. The room temperature PL spectra of HVPE grown Er:GaN epilayers resolved as many as 11 and seven emission lines in the 1.5 µm and 1.0 µm wavelength regions, respectively, corresponding to the intra-4f shell transitions between Stark levels from the first (4I13/2) and the second (4I11/2) excited states to the ground state (4I15/2) of Er3+ in GaN. The observed peak positions of these transitions enabled the construction of the detailed energy levels in Er:GaN. The results agree well with those of the calculation based on a crystal field analysis. Precise determination of the detailed energy levels of the Stark levels in the 4I11/2, 4I13/2, and 4I15/5 states is critically important for the realization of HELs based on Er:GaN.
Highlights
An optical gain medium is the heart of solid-state high energy laser (HEL) systems, which have been investigated for decades due to their numerous applications in communication, defense, manufacturing, and medicine.1 The most common gain material for solidstate high energy lasers (HELs) today is the synthetic garnet such as YAG doped with neodymium (Nd:YAG) emitting at 1.06 μm
The x-ray diffraction (XRD) rocking curve of the (0002) peak is shown in Fig. 2(b) and has a full-width at half-maximum (FWHM) of 1400 arcsec, indicating that Erbium doped GaN (Er):GaN grown by hydride vapor phase epitaxy (HVPE) has a reasonable crystalline quality
It was observed that Er:GaN epilayers produced by HVPE in the present work exhibit unprecedented rich spectroscopic features, from which detailed Stark levels in the 4I11/2, 4I13/2, and 4I15/2 states of Er3+ ions in GaN were extracted
Summary
An optical gain medium is the heart of solid-state high energy laser (HEL) systems, which have been investigated for decades due to their numerous applications in communication, defense, manufacturing, and medicine. The most common gain material for solidstate HELs today is the synthetic garnet such as YAG doped with neodymium (Nd:YAG) emitting at 1.06 μm. An optical gain medium is the heart of solid-state high energy laser (HEL) systems, which have been investigated for decades due to their numerous applications in communication, defense, manufacturing, and medicine.. Metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are the two major techniques used for the growth of Er:GaN epitaxial thin films with a typical thickness of less than 5 μm and low growth rate of about 1 μm/h.7,14–34. For HEL applications, Er:GaN with large thicknesses and, high growth rates is needed. Er:GaN bulk crystals have been synthesized recently via the hydride vapor phase epitaxy (HVPE) technique at high growth rates (up to ∼200 μm/h).. The basic properties of Er doped GaN thin films grown by MOCVD and MBE have been widely reported, studies on the optical properties of Er:GaN grown by HVPE have been limited. Er:GaN bulk crystals have been synthesized recently via the hydride vapor phase epitaxy (HVPE) technique at high growth rates (up to ∼200 μm/h). the basic properties of Er doped GaN thin films grown by MOCVD and MBE have been widely reported, studies on the optical properties of Er:GaN grown by HVPE have been limited.
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