ZnMgSSe/ZnSe/CdSe quantum dot heterostructures for green laser applications G.P. Yablonskii a, ⁎, E.V. Lutsenko a , A.G. Vainilovich a , V.N. Pavlovskii a , S.V. Ivanov b , I.V. Sedova b , S.V. Sorokin b , P.S. Kop'ev b a Stepanov Institute of Physics of NASB, Independence Ave. 68, 220072 Minsk, Belarus b Ioffe Physical Technical Institute, Polytekhnicheskaya 26, 19402 St. Petersburg, Russia abstract article info Article history: Received 18 May 2010 Available online 9 June 2010 Keywords: Laser; Heterostructure; Quantum well; Quantum dot; Laser converter Cd(Zn)Se/ZnSSe/ZnMgSSe laser heterostructures with an asymmetrical ZnSSe/ZnSe supperlattice waveguide, and multiple (up to 9) electronically-coupled CdSe quantum dot sheets in the active region were designed and grown by molecular beam epitaxy. Internal quantum efficiency η i , internal loss α i , transparency threshold J T and characteristic gain ΓG 0 were found to be: 58.5%, 7 cm -1 , 1.78 kW/cm 2 , and 194 cm -1 , respectively, in a laser heterostructure with 9 electronically-coupled CdSe quantum dot active layers. A violet-green integrated laser converter with the output pulse power up to 50 mW was fabricated on the basis of the Cd(Zn)Se/ZnSSe/ZnMgSSe quantum dot laser heterostructure. The heterostructures were optically pumped by emission of a violet (λ = 416 nm) commercial InGaN/GaN pulsed laser diode. The ways for further laser threshold reduction and increasing the efficiency are discussed. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Compact green semiconductor lasers with a long operation time can be used for numerous applications such as local networks, space- underwater communication, lidars and navigation, projection TV, reprographics (laser printers, exposition of photographic media), laser and target pointers, sensors, etc. The most appropriate candidates, lasers diodes based on ZnSe heterostructures were fabricated for the first time in the early 90s [1,2], and up to now, their lifetime is still limited by ∼ 400 h in a cw regime [3] because of the non-stable nature of the nitrogen acceptor. The mechanism responsible for the slow degradation of ZnSe-based lasers is most often explained by compensating donor centers, i.e. nitrogen interstitial atoms which diffuse into the active region from a p-type doped layer during laser operation. In addition, the shallow nitrogen acceptor is unstable and can transform into an interstitial center and create a mobile charged complex with a selenium vacancy [4–6]. The main competitor of the II–VI-based lasers for a green spectral region are InGaN/GaN laser diodes. However, an increase in the In content in InGaN quantum wells (QWs) promotes a fast rise of the composition inhomogeneity with a formation of In-rich nanoscale clusters and a significant increase in the density of non-radiative defects. It is only violet and blue regions of a visible spectrum that have been covered by the InGaN/GaN laser diodes (LDs) during the 13 years of active research since the first violet LD was fabricated [7]. The recent progress in the development of GaN based green LDs is associated with the growth of heterostructures on freestanding m-plane GaN substrates [8–10]. The maximal achieved operation wavelength at room temperature (RT) in the pulse mode is as high as 531 nm with the laser threshold of ∼ 8 kA/cm 2 . Diode-pumped solid-state lasers with frequency doubling are now the most powerful lasers in the green spectral range. However, the narrow range of operational temperature as well as a fixed lasing wavelength (λ = 532 nm) are essential shortcomings of these lasers for a number of applications. Therefore, semiconductor lasers with both pulsed optical and electron beam pumping which do not require a p–n junction and ohmic contacts and, thus, are free from the problems limiting the lifetime of LDs, still attract considerable interest for the development of commercial green lasers. It has been shown that undoped ZnSe-based laser structures with ZnCdSe QW and CdSe quantum dots (QD) active region demonstrate a high degradation stability under optical and electron beam pumping [11,12]. The creation of integrated laser converters containing II–VI-based green-emitting laser heterostructures optically pumped by emission of InGaN LD looks as a prospective idea to overcome the lifetime problem of II–VI lasers. The possibility to use optically-pumped InGaN/GaN (λ = 452–458 nm) multiple QW heterostructures grown by metal organic vapor phase epitaxy on Si (111) substrates at AIXTRON AG for optical excitation of green Cd(Zn)Se/ZnSSe/ZnMgSSe laser structures was reported for the first time in [13,14]. II–VI laser heterostructures grown by molecular beam epitaxy (MBE) were pumped in a transverse geometry without an additional optical lens. The laser chips were fabricated by cleaving the heterostructure along the basal planes without any special mirror deposition. The energy conversion coefficient of such an integral optical converter was as high as ∼ 1% at room temperature. The Cd(Zn)Se/ZnSSe/ZnMgSSe Journal of Non-Crystalline Solids 356 (2010) 1928–1934 ⁎ Corrresponding author. E-mail address: g.yablonskii@ifanbel.bas-net.by (G.P. Yablonskii). 0022-3093/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2010.05.038 Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol