Effect of additionally introduced Zn and Eu dopants on the photoluminescence spectra of Er-Doped GaN crystals
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TRONIC AND OPTICAL PROPERTIES OF SEMICONDUCTORS
Effect of Additionally Introduced Zn and Eu Dopants on the Photoluminescence Spectra of Er-Doped GaN Crystals M. M. Mezdrogina^, V. V. Krivolapchuk^^, V. N. Petrov, S. N. Rodin, and A. V. Cherenkov Ioffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia ^e-mail: [email protected] ^^e-mail: [email protected] Submitted June 9, 2006; accepted for publication June 15, 2006
Abstract—It is shown that the effect of dopants on the photoluminescence spectrum depends on the conductivity type of the initial GaN crystals. Sensitization of emission is observed in wurtzite p-GaN crystals doped with Er. The same effect was previously observed in such crystals doped with Eu and Zn. In n-type GaN crystals sequentially doped with Eu, Zn, and Er, emission is observed in the visible (λ = 360–440 and 530–560 nm) and IR (λ = 1.54 µm) spectral regions. PACS numbers: 78.55.Cr, 61.72.Vv DOI: 10.1134/S1063782606120025
1. INTRODUCTION Extensive studies of the GaN direct-gap wide-gap semiconductor grown on a silicon (c-Si) substrate and doped with rare-earth ions (REIs), specifically, with Eu, have culminated in the detection of laser emission at the wavelength λ = 620 nm at room temperature [1, 2]. These studies are of great importance now, because doping of GaN crystals grown on c-Si substrates provides an opportunity to observe laser emission within a wide spectral range (from the ultraviolet to infrared regions) at room temperature. The intracenter f–f transition in the Er dopant (I13/2–I15/2) occurs at the wavelength λ = 1.54 µm, which coincides with the wavelength that corresponds to the minimum losses in quartz fiber components of optical communication systems. This fact stimulated extensive investigations of the effect of Er dopants introduced into the GaN wide-gap semiconductor matrix (GaN:Er) [3, 4] on the luminescence intensity. At the present time, it is known that the intensity of intracenter transitions in REIs is controlled by the following factors: the optimal concentration of optically active centers, the occupancy of the emitting states that depends on the transfer of nonequilibrium charge carriers from the semiconductor matrix to REIs, and the excitation intensity and wavelength. At the same time, it should be noted that, in spite of extensive studies of this problem in the last decade, the attempts to obtain emission at the wavelength λ = 1.54 µm at an intensity sufficient for practical applications have been as yet unsuccessful. One of the causes of such a situation is the rather complicated and hardly controllable structure of the dopant complexes containing REIs, specifically, Er. As a result, the above-mentioned factors (the concen-
tration of optically active centers, the efficiency of their occupation, and the oscillator strength) are also uncontrollable. Therefore, in a number of studies, the Er-containing complexes are classified as “red” and “violet” ones, depending on the efficiency of their emission as a functio
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