Electron Beam Pumped MQW InGaN/GaN Laser
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Internet Journal o f
Nitride S emiconductor Research
Volume 2, Article 38
Electron Beam Pumped MQW InGaN/GaN Laser V.I. Kozlovsky, A.B. Krysa, Y.K. Skyasyrsky, Y.M. Popov P.N. Lebedev Physical Institute A. Abare, M.P. Mack, S. Keller, U. K. Mishra, L. Coldren, Steven DenBaars Electrical and Computer Engineering and Materials Departments, University of California, Santa Barbara Michael D. Tiberi , T. George Principia Optics, Inc. This article was received on and accepted on September 17, 1997.
Abstract E-beam pumped lasers are attractive for Laser Cathode Ray Tubes (LCRT) in projection displays and a variety of applications typically associated with optically pumped lasers. For the first time an InGaN/GaN multiple quantum well (MQW) in-plane laser pumped by surface normal pulse and scanning electron beams was demonstrated. Pumping at room temperature (RT) and 80 K showed peak stimulated emission wavelengths of 402 and 409 nm with a full width half maximum (FWHM) of 0.6 nm and 1.2 nm, respectively. The threshold electron beam current densities have been estimated as 60 A/cm2 for 35 keV electron energy at 80 K using scanning e-beam pumping and 200-300 A/cm2 at RT using pulsed e-beam pumping with a maximum electron energy of 150 keV. At 80 K, light output of 150 mW was measured out of one facet at an e-beam current of 1.7 mA.
1. Introduction Recent efforts in the development of III-V nitride semiconductors has led to the commercial production of high-brightness blue and green light-emitting diodes (LEDs) [1] and to the demonstration of RT continuous wave (CW) laser diodes [2] [3]. Another application for nitride technology is e-beam pumped lasers for display technology [4] [5]. The LCRT is promising as a stand alone projection display device [6] [7], as a high power light source for existing projection displays and as an ultraviolet light source for photolithography [8]. The LCRT would typically operate in a vertically pumped configuration. However, due to difficulty of fabricating suitable vertical cavity structures we have initially investigated in-plane laser cavities. Further studies are underway to prepare vertical cavity samples. Short wavelength vertical cavity (VCL) electron beam pumped lasers have been demonstrated using II-VI bulk single crystal compounds: ZnSe (470 nm at RT) [9], ZnO (375 nm at 80 K) [10], and ZnS (330 nm at 80 K) [11]. In the VCL geometry, RT thresholds are still too high for commercial applications of these devices. Significant reduction in the threshold current is expected when bulk active regions are replaced by heterostructures employing MQW active. Heterostructures in the II-VI ZnSe material system have been demonstrated (493 nm at RT) [12] but they suffer from short lifetimes of several hours due to defect propagation. We believe that the III-V nitride compounds are ideally suited for short wavelength laser screens because of their greater thermal conductivity and superior stability under high excitation levels.
2. Experiment The samples were grown by MOCVD on (0001) sapphire. T
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