Optical Characterization of Erbium Doped III-Nitrides Prepared by Metalorganic Molecular Beam Epitaxy
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 4S1, G1l.6 (1999) ABSTRACT We are currently engaged in a systematic study of the optical properties of Er doped IIInitrides prepared by metalorganic molecular beam epitaxy (MOMBE). Under below-gap excitation it was observed that GaN: Er samples with [O]~1020 cm-3 and [C]-10 2' cm-3 luminesce at 1540 nm with an intensity of more than two orders of magnitude greater than samples with low oxygen and carbon concentrations (< 10'9 cm 3). Associated with the different oxygen and carbon concentrations were different thermal quenching behaviors and below-gap absorption bands. Interestingly, for above-gap excitation only small differences in absolute Er3" PL intensity and quenching behavior were observed for samples of varying 0 and C content. Initial lifetime studies were performed and showed a rather unusual short decay time of -100 ýts at room temperature. In order to gain more insight in the Er 3" PL, a comparison of the integrated PL intensity and lifetime was performed for the temperature range 15-500K. The result reveals that the Er 3 PL quenches above room temperature due to the onset of non-radiative decay and the reduction in excitation efficiency. All samples were also investigated for visible luminescence. Red luminescence was observed from GaN: Er on sapphire substrates under below-gap excitation.
INTRODUCTION Rare earth doped semiconductors have been studies for more than a decade because of the possibility to develop compact and efficient electroluminescence devices. ,23A4 Trivalent Erbium ions (Er3+) are of special interest because they exhibit an atomic-like transition at 1540nm, which corresponds to the low-loss window of silica-based optical fibers. Electroluminescence devices based on Er doped Si and GaAs were reported, however, their efficiency was too low for practical applications. 34 An important step forward in the field of Er doped semiconductors was the observation that the room-temperature Er 3+ photoluminescence (PL) intensity strongly depends on the bandgap of the host materials. It was found that for larger bandgap energy, there is less detrimental temperature quenching of Er 3, PL occurring.5 ' 6 Therefore, doping Er3+ ions into wide gap semiconductors is a promising approach to overcome the thermal quenching of Er3 + PL. Consequently, current research efforts focus on studying Er 3' doped into wide bandgap semiconductors such as SiC and GaN. 75 First results on the observation of 1.54 itm photoluminescence from Er implanted GaN and AIN were reported by Wilson et al. 9 Subsequently, other research groups reported results of photoluminescence, cathodoluminescence, and electroluminescence (EL) studies of Er implanted GaN. 10,11,12.13 The goal for practical device applications is to incorporate Er3+ ions during epitaxial growth. Doping during growth has several advantages over ion implantation including the absence of implantation damage, unlimited layer thickness, and a more homogenous doping profile. In-situ Er doping of AIN using m
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