TY - JOUR
T1 - Influences of two-step growth and off-angle Ge substrate on crystalline quality of GaAs buffer layers grown by MOVPE
AU - Wanarattikan, Pornsiri
AU - Sanorpim, Sakuntam
AU - Denchitcharoen, Somyod
AU - Uesugi, Kenjiro
AU - Kuboya, Shigeyuki
AU - Onabe, Kentaro
N1 - Funding Information:
This work has been supported by the Ratchadaphiseksomphot Endowment Fund of Chulalongkron University ( RES560530229-EN ). P. W and S. D acknowledge financial support from the Department of Physics, Faculty of Science, King Mongkut’s University of Technology Thonburi and Huachiew Chalermprakiet University . The authors would like to gratefully acknowledge National Metal and Materials Technology Center (MTEC) for the cooperation in TEM measurements.
Publisher Copyright:
© 2014 Elsevier B.V. All rights reserved.
PY - 2015/3/15
Y1 - 2015/3/15
N2 - GaAs buffer layers were grown on off-angle Ge substrates with a two-step growth process by metalorganic vapor phase epitaxy in order to prepare a high quality buffer layer for the InGaAsN p-i-n solar-cell structure. In our contribution, we present results from the optimized two-step growth of GaAs buffer layers, namely with a low-temperature step at 470 C and a high-temperature step at 580 C, combined with the use of Ge substrates misoriented by 4 and 6 towards [1 1 0]. HRXRD results showed that by using the off-angle substrates, the FWHM of (0 0 4) rocking curves was decreased to 6.7 sec, which is about 4 times the FWHM of the GaAs commercial substrate. A decreased FWHM indicates a narrower distribution of crystal orientation. Furthermore, a smooth surface with a RMS roughness of 0.7 nm was clearly observed by AFM. Cross-sectional dark-field TEM images showed the GaAs buffer layer with 20-30 nm diamond-shaped anti-phase domains (APDs) at the GaAs/Ge interface, followed by APDs-free GaAs regions on the 6 off-angle Ge substrate. However, anti-phase boundaries were generated along the [0 0 1] direction for the buffer layer on the on-axis substrate. Our results demonstrated that the use of 6 off-angle Ge substrate and a two-step growth process allow the suppression of APDs in the GaAs buffer layer.
AB - GaAs buffer layers were grown on off-angle Ge substrates with a two-step growth process by metalorganic vapor phase epitaxy in order to prepare a high quality buffer layer for the InGaAsN p-i-n solar-cell structure. In our contribution, we present results from the optimized two-step growth of GaAs buffer layers, namely with a low-temperature step at 470 C and a high-temperature step at 580 C, combined with the use of Ge substrates misoriented by 4 and 6 towards [1 1 0]. HRXRD results showed that by using the off-angle substrates, the FWHM of (0 0 4) rocking curves was decreased to 6.7 sec, which is about 4 times the FWHM of the GaAs commercial substrate. A decreased FWHM indicates a narrower distribution of crystal orientation. Furthermore, a smooth surface with a RMS roughness of 0.7 nm was clearly observed by AFM. Cross-sectional dark-field TEM images showed the GaAs buffer layer with 20-30 nm diamond-shaped anti-phase domains (APDs) at the GaAs/Ge interface, followed by APDs-free GaAs regions on the 6 off-angle Ge substrate. However, anti-phase boundaries were generated along the [0 0 1] direction for the buffer layer on the on-axis substrate. Our results demonstrated that the use of 6 off-angle Ge substrate and a two-step growth process allow the suppression of APDs in the GaAs buffer layer.
KW - A1. High resolution X-ray diffraction
KW - A3. Metaloganic vapor phase epitaxy
KW - B2. Semiconducting gallium arsenide
KW - B2. Semiconducting germanium
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U2 - 10.1016/j.jcrysgro.2014.11.027
DO - 10.1016/j.jcrysgro.2014.11.027
M3 - Article
AN - SCOPUS:84922483883
VL - 414
SP - 15
EP - 20
JO - Journal of Crystal Growth
JF - Journal of Crystal Growth
SN - 0022-0248
ER -