Sains Malaysiana 49(10)(2020): 2559-2564

http://dx.doi.org/10.17576/jsm-2020-4910-21

Photoluminescence and Raman Scattering of GaAs_1-xBi_x Alloy

(Kefotopendarcahayaan dan Serakan Raman pada Aloi GaAs_1-xBi_x)

L. HASANAH¹, C. JULIAN¹, B. MULYANTI², A. ARANSA¹, R. SUMATRI¹, M.H. JOHARI³, J.P.R. DAVID⁴ & A.R. MOHMAD³*

¹Department of Physics Education, Universitas Pendidikan Indonesia, Dr. Setiabudhi St. No. 229, 40154, Bandung, Indonesia

²Department of Electrical Engineering Education, Universitas Pendidikan Indonesia, Dr. Setiabudhi St. No. 229, 40154 Bandung, Indonesia

³Institute of Microengineering and Nanoelectronics, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

⁴Department of Electronics and Electrical Engineering, University of Sheffield, Mappin Street S1 3JD, Sheffield, United Kingdom

Diserahkan: 4 Mac 2020/Diterima: 17 April 2020

ABSTRACT

Photoluminescence (PL) and Raman spectra of GaAs_1-xBi_x samples grown at different rates (0.09 to 0.5 µm/h) were investigated. The PL peak wavelength initially redshifted with the increase of growth rate and reached the longest wavelength (1158 nm) for sample grown at 0.23 µm/h. This is followed by PL peak wavelength blueshift for higher growth rates. The Raman data show peaks at 162, 228, 270, and 295 cm^-1 which can be attributed to GaAs like phonons. GaBi like vibrational modes were also observed at 183 and 213 cm^-1. However, the intensity of Bi induced phonons is significantly weaker compared to GaAs due to low concentration of Bi compared to As and thin GaAs_1-xBi_x epilayer. The PL data and GaAs transverse optical (TO) to longitudinal optical (LO) phonons intensity ratio indicate that Bi concentration is highly dependent on the growth rate and the highest Bi concentration was obtained by sample grown at 0.23 µm/h. It is found that the full-width-at-half-maximum (FWHM) of GaAs LO mode increases significantly for samples grown at high growth rates suggesting crystal quality degradation due to lack of surfactant effects.

Keywords: GaAsBi; photoluminescence; Raman spectroscopy

ABSTRAK

Kefotopendarcahayaan (PL) dan spektrum Raman daripada sampel GaAs_1-xBi_x yang ditumbuhkan pada kadar berbeza (0.09 hingga 0.5 µm/jam) telah dikaji. Pada mulanya, panjang gelombang puncak PL mengalami anjakan merah dengan peningkatan kadar pertumbuhan dan mencapai panjang gelombang tertinggi iaitu 1158 nm untuk sampel yang ditumbuh pada kadar 0.23 µm/jam. Ini diikuti oleh anjakan biru pada kadar pertumbuhan yang lebih tinggi. Data Raman menunjukkan kehadiran beberapa puncak pada nombor gelombang 162, 228, 270 dan 295 cm^-1 yang disebabkan oleh fonon GaAs. Selain itu, mod getaran GaBi juga dapat diperhatikan pada 183 dan 213 cm^-1. Namun, keamatan fonon GaBi jauh lebih lemah berbanding GaAs disebabkan kepekatan Bi yang rendah berbanding As dan lapisan GaAs_1-xBi_x yang nipis. Data PL dan nisbah keamatan fonon optik melintang (TO) kepada fonon optik membujur (LO) GaAs menunjukkan bahawa kepekatan Bi sangat bergantung kepada kadar pertumbuhan dan kepekatan Bi yang tertinggi diperoleh oleh sampel yang ditumbuh pada kadar 0.23 µm/jam. Kajian ini mendapati bahawa nilai FWHM untuk fonon LO GaAs meningkat dengan ketara untuk sampel yang ditumbuh dengan kadar pertumbuhan yang tinggi dan ini menunjukkan kemerosotan kualiti kristal disebabkan oleh pengurangan kesan surfaktan.

Kata kunci: GaAsBi; kefotopendarcahayaan; spektroskopi Raman

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*Pengarang untuk surat-menyurat; email: armohmad@ukm.edu.my