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

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

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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

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SLIDE 1

“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

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

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  • Introduction
  • Wafer Details
  • GaAsBi HRXRD
  • Power Dependent PL
  • Temperature Dependent PL
  • Room temperature FWHM
  • Summary

Outline

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  • Bi-containing alloy for optoelectronics and

spintronics devices.

  • We want devices to be cheap, reliable,

temperature insensitive etc.

  • PL to assess GaAsBi quality.

Introduction

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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 GaAs1-xBix 160 GaAs buffer 80 S.I or n+ (100) GaAs substrate

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GaAsBi HRXRD

  • [Bi] = 0 – 0.058
  • Fringes clearly observed for [Bi] = 0.032
  • No traces of Bi on non-Bi wafers grown afterwards.

Sample Bi content B1 B2 0.022 BA 0.032 B6 0.058

1

1 0

2

1 0

3

1 0

4

1 0

5

1 0

6

1 0

7

1 0

8

1 0

9

1 0

  • 2 5 0 0
  • 2 0 0 0
  • 1 5 0 0
  • 1 0 0 0
  • 5 0 0

5 0 0 1 0 0 0 I n t e n s i t y ( c p s ) O M E G A -2 T H E T A (a rc s e c ) 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 *

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Power dependent PL

  • 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.

800 900 1000 1100 1200 1300 0.01 0.1 1

Normalised PL Intensity, a.u Wavelength, nm 0.02 mW 0.2 mW 2 mW 20 mW 200 mW Power Dependent PL at 10 K

Power Dependent PL at 10 K

Excitation Power, mW

0.01 0.1 1 10 100 1000

PL Peak Energy, eV

1.16 1.18 1.20 1.22 1.24 1.26 1.28

FWHM, nm

40 50 60 70 80 90 100 110 PL Peak Energy FWHM

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Power dependent PL

  • 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).

Excitation Power, mW

0.01 0.1 1 10 100 1000 10000

Integrated PL Intensity, a.u

103 104 105 106 107 108 109 1010 1011 10K 77K 150K RT m = 1.0 m = 1.1 m = 1.6 m = 1.9

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Temperature dependent PL

  • 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.

Source Bi content a (meV/K) GaAs 0.46 Pettinari et al 0.019 0.36 Sheffield BA 0.032 0.31 Imhof et al 0.04-0.05 0.27

Temperature, K

50 100 150 200 250 300

PL Peak Energy, eV

1.14 1.16 1.18 1.20 1.22 1.24 1.26 1.28 200 mW 20 mW 2 mW

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Temperature dependent FWHM

  • 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.

Temperature, K

50 100 150 200 250 300

FWHM, nm

50 60 70 80 90 100 200 mW 20 mW

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Room Temperature FWHM

Source Bi content (%) FWHM (nm) p (nm) Tixier et al 2003 0.013 101 979 Lu et al 2009 0.014 85

  • Sheffield B2

0.022 69 (45@10K) 990 Lu et al 2009 0.023 107 1016 Bertulis et al 2006 0.029 195 1055 Tixier et al 2003 0.031 118.8 1078 Sheffield BA 0.032 65 (51@10K) 1038 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.

800 900 1000 1100 1200 1300 1400 0.0 0.2 0.4 0.6 0.8 1.0

Normalised PL Intensity, (a.u) Wavelength, (nm)

RT PL, P = 200 mW (600 W/cm2)

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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 GaAs0.973Bi0.032 with FWHM = 65 nm (75 meV) at RT.

Possibility of growing high quality GaAsBi.

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