Effects of Si doping on optical properties of GaN epitaxial layers

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1 (123) 31 Effects of Si doping on optical properties of GaN epitaxial layers Chiharu SASAKI (Department of Electrical and Electronic Engineering) Tatsuya YAMASHITA (Department of Electrical and Electronic Engineering) Yoichi YAMADA (Department of Electrical and Electronic Engineering) Tsunemasa TAGUCHI (Department of Electrical and Electronic Engineering) Optical properties of and GaN epitaxial layers grown by MOCVD have been studied by means of temperature-dependent and time-resolved photoluminescence spectroscopy. The intensity of band edge emission from epitaxial layers was approximately one order of magnitude stronger than that from epitaxial layers at. It was found that nonradiative recombination in GaN epitaxial layers was suppressed by Si-doping. The effects of Si-doping on luminescence properties of GaN epitaxial layers are discussed as a function of electron concentration. Key Words : GaN, Si-doping, Time-resolved photoluminescence, Lifetime GaN GaAs ZnSe InGaN InGaN 1, ) GaN InGaN Si 3) InGaN cm -2 InGaN 4) InGaN In InGaN

2 32 (124) cm Fig. 1. Photoluminescence spectra at taken from and GaN epitaxial layers. Bound-to-Free x cm -3 Bound-to-Free Fig. 2. Photoluminescence spectra at taken from and GaN epitaxial layers. x 2.4 x 30 Si 250 khz GaN Si GaN GaN Si MOCVD Metalorganic Chemical Vapor Deposition GaN cm -3 A B Si GaN cm -3 PL Photoluminescence Si GaN PL TRPL Time-resolved photoluminescence Si PL GaN PL He-Cd 325 nm CCD 1 2 PL ps s ns Si 10-9 s 5) GaN PL GaN 3 6) 266 nm 200 fs s Si Vol.50 No.2 (2000) 1 2 GaN PL GaN PL A n = 2 Xe

3 (125) 33 x 8 x13 x 206 x K 50 K 130 K x 4 x x K 100 K 200 K Fig. 3. Temperature dependence of photoluminescence spectra taken from an GaN epitaxial layer Fig. 4. Temperature dependence of photoluminescence spectra taken from a GaN epitaxial layer. PL 80 2 GaN PL 60 Si Bound-to-free GaN 40 GaN PL PL 32 K A Fig. 5. Temperature dependence of full-width at 120 K half-maximum of photoluminescence spectra taken from and GaN epitaxial layers. GaN A Si GaN 5 PL 4 A LO Si GaN PL 7) Si GaN A GaN Si 5 FWHM (mev)

4 34 (126) Fig. 6. Time-resolved photoluminescence spectra from GaN epitaxial layers at. Si GaN cm -3 GaN cm Si 500 Bound-to-free GaN Si PL 6 GaN (1) t t I( t) = a exp + b exp (1) Fig. 8. Temperature dependence of radiative and τ 1 τ 2 nonradiative recombination lifetime in a a b 1 2 GaN epitaxial layer. 8, 9) 6 PL(T) Si rad(t) non-rad(t) cm -3 GaN = + (2) τ ( ) ( ) ( ) PL T τ rad T τ non rad T Si GaN PL PL η(t) PL Vol.50 No.2 (2000) 130 ps 82 ps 69 ps 350 ps 330 ps 270 ps cm TIME DELAY (ps) LIFE TIME (ps) PL rad non-rad Fig. 7. Temperature dependence of radiative and nonradiative recombination lifetime in an GaN epitaxial layer. LIFE TIME (ps) PL rad non-rad

5 (127) 35 τ non -rad ( T ) η( T ) = (3) Si GaN τ rad ( T ) + τ non -rad ( T ) PL PL I const 1 (4) Si GaN I( T ) η ( T ) = (4) I const (2) (4) rad(t) non-rad(t) 7 8 GaN Si GaN MITI/NEDO/JRCM ( "21 ") GaN Si GaN GaN Si GaN 1) S. Nakamura, M. Senoh, S. Nagahama, T. Matsushita, H. Kiyoku, Y. Sugimoto, T. Kozaki, H. Umemoto, M. GaN 10 ns Sano, and T. Mukai, Jpn. J. Appl. Phys., Part 2 38, Si GaN 1 ns L226 (1999). Si 2), 68, 793 (1999). Si GaN 3), 68, 787 (1999). 4) Y. Yamada, T. Taguchi, F. Sasaki, S. Kobayashi, and T. Tani, J. Cryst. Growth 189/190, 611 (1998). GaN 5) I. H. Lee, J. J. Lee, P. Kung, F. J. Sanchez, and M. Razeghi, Appl. Phys. Lett. 74, 102 (1999). GaN Si GaN 6) A. A. Yamaguchi, K. Kobayashi, A. Sakai, Y Si Mochizuki, H. Sunakawa, and A. Usui, 2nd Intern. PL 1 Symp. on Blue Laser and Light Emitting Diodes, Chiba, Japan, 692 (1998). 7) J. Lee, E. S. Koteles, and M. O. Vassell, Phys. Rev. B 33, 5512 (1986). 8),,,,, GaN Si GaN PL GaN,, PL C- 81, 78 (1998). 9) Y. Narukawa, Y. Kawakami, Sg. Fujita, and S. Si GaN Nakamura, Phys. Rev. B 59, (1999). PL Si GaN GaN 1