Photoluminescence Investigation of Bulk GaAsBi on GaAs A. R. - PowerPoint PPT Presentation

“Photoluminescence Investigation of Bulk GaAsBi on GaAs” A. R. Mohmad, F. Bastiman, J. S. Ng, J. P. R. David University of Sheffield, UK S. Jin, S. J. Sweeney University of Surrey, UK

2 Outline • Introduction • Wafer Details • GaAsBi HRXRD • Power Dependent PL • Temperature Dependent PL • Room temperature FWHM • Summary 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

3 Introduction • Bi-containing alloy for optoelectronics and spintronics devices. • We want devices to be cheap, reliable, temperature insensitive etc. • PL to assess GaAsBi quality. 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

4 Wafer Details • Omicron STM-MBE • Wafer size: 3.5 x 5 mm • Ga assisted oxide removal to avoid thick buffer. Material Thickness (nm) GaAs cap 80 GaAs 1-x Bi x 160 GaAs buffer 80 S.I or n+ (100) GaAs substrate 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

5 GaAsBi HRXRD S T A 0 B 1 _ 0 2 a a 0 0 1 .X 0 1 S T A 0 B 2 _ 0 2 a a 0 0 1 .X 0 1 S T A 0 B A _ 0 1 a a 0 0 1 .X 0 1 S T A 0 B 6 _ 0 1 a a 0 0 1 .X 0 1 * 9 1 0 8 1 0 Sample Bi content 7 1 0 I n t e n s i t y ( c p s ) B1 0 1 0 6 B2 0.022 1 0 5 1 0 4 BA 0.032 1 0 3 B6 0.058 1 0 2 1 1 0 -2 5 0 0 -2 0 0 0 -1 5 0 0 -1 0 0 0 -5 0 0 0 5 0 0 1 0 0 0 O M E G A -2 T H E T A (a rc s e c ) • [Bi] = 0 – 0.058 • Fringes clearly observed for [Bi] = 0.032 • No traces of Bi on non-Bi wafers grown afterwards. 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

6 Power dependent PL Power Dependent PL at 10 K Power Dependent PL at 10 K 1 0.02 mW 0.2 mW 1.28 110 2 mW 20 mW Normalised PL Intensity, a.u 100 1.26 200 mW PL Peak Energy 0.1 90 PL Peak Energy, eV FWHM 1.24 FWHM, nm 80 1.22 70 0.01 1.20 60 1.18 50 1.16 40 800 900 1000 1100 1200 1300 0.01 0.1 1 10 100 1000 Wavelength, nm Excitation Power, mW • At RT, PL peak energy is independent of the excitation power. • PL peak energy is blue-shifted with increasing power at 10 K. • FWHM reduces as power is increased at 10 K. 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

7 Power dependent PL 10 11 10K 10 10 77K 150K Integrated PL Intensity, a.u RT 10 9 10 8 10 7 m = 1.0 10 6 m = 1.1 10 5 m = 1.9 m = 1.6 10 4 10 3 0.01 0.1 1 10 100 1000 10000 Excitation Power, mW • At 10 K, radiative recombination is dominant (m=1). • Non-radiative recombination dominated at RT (m~2). • Mixture of both at intermediate temperatures (m=1-2). 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

8 Temperature dependent PL 1.28 200 mW Source Bi content a (meV/K) 1.26 20 mW 2 mW GaAs 0 0.46 1.24 PL Peak Energy, eV Pettinari et al 0.019 0.36 1.22 Sheffield BA 0.032 0.31 1.20 Imhof et al 0.04-0.05 0.27 1.18 1.16 1.14 0 50 100 150 200 250 300 Temperature, K • S-shape behaviour observed – localisation. • Localisation potential = 15 meV. • Expect a to decrease with increasing [Bi]. (GaNAsBi; 0.15 meV/K, [Bi]=0.026). • Origin of peak at 1.22 eV (10 K) is unknown. 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

9 Temperature dependent FWHM 100 200 mW 20 mW 90 FWHM, nm 80 70 60 50 0 50 100 150 200 250 300 Temperature, K • FWHM maxima due to increase in exciton mobility. • kT@160 K = 14 meV. Consistent with localisation energy (15 meV). • FWHM increase at T>160 K due to thermal distributions and phonon scattering. 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

10 Room Temperature FWHM  p RT PL, P = 200 mW (600 W/cm 2 ) Source Bi content FWHM (%) (nm) (nm) Tixier et al 2003 0.013 101 979 1.0 Lu et al 2009 0.014 85 - Normalised PL Intensity, (a.u) 0.8 Sheffield B2 0.022 69 (45@10K) 990 0.6 Lu et al 2009 0.023 107 1016 0.4 Bertulis et al 0.029 195 1055 2006 0.2 Tixier et al 2003 0.031 118.8 1078 0.0 Sheffield BA 0.032 65 (51@10K) 1038 800 900 1000 1100 1200 1300 1400 Wavelength, (nm) Lu et al 2009 0.036 130 - • FWHM of 65 nm (75 meV) > ~45 meV due to thermal distribution broadening. Wide FWHM is due to Bi fluctuations. • Narrowest RT FWHM compared with reported values in literature. 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

11 Conclusions • HRXRD shows clear fringes for [Bi] up to 3.2%, , indication of good interface. • Radiative recombination is dominant at 10 K while non-radiative recombination dominated at RT. Mixture of both at intermediate temperatures. • Evidence of localisation effects: - PL peak energy dependent on excitation power. - S-shape with localisation potential of 15 meV. - FWHM peaking at 100 K. • a = 0.31 meV/K between 150 K <T< 280 K. • Demonstrated GaAs 0.973 Bi 0.032 with FWHM = 65 nm (75 meV) at RT. Possibility of growing high quality GaAsBi. 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA

12 14-16 th July 2010 1 st International Workshop on Bismuth-Containing Semiconductors, Michigan, USA