Raman scattering studies of strain effects in (100) and (311)B GaAs1−xBix epitaxial layers

• Published in: Journal of applied physics 2013-11, Vol.114 (19)
• Main Authors: Steele, J A, Lewis, R A, Henini, M, Lemine, O M, Alkaoud, A
• Format: Article
• Language: English
• Subjects: Alloying effects; Applied physics; Crystal defects; Crystal growth; Epitaxial layers; Lattice strain; Peak frequency; Phonons; Raman spectra; Red shift; Substrates; X ray spectra; X-ray diffraction
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4831947

We report room-temperature Raman studies of strained (100) and (311)B GaAs1−xBix epitaxial layers for x ≤ 0.039. The Raman spectra exhibit a two-mode behavior, as well as disorder-activated GaAs-like phonons. The experimental results show that the GaAs-like LO(Γ) mode experiences a strong composition-dependent redshift as a result of alloying. The peak frequency decreases linearly from the value for pure GaAs (∼293 cm−1) with the alloyed Bi fraction x and the introduced in-plane lattice strain ε∥, by ΔωLO=Δωalloy−Δωstrain. X-ray diffraction measurements are used to determine x and ε∥ allowing Δωalloy to be decoupled and is estimated to be −12(±4) cm−1/x for (100) GaAs1−xBix. ΔωLO is measured to be roughly double for samples grown on (311)B-oriented substrates to that of (100) GaAs. This large difference in redshift is accounted for by examining the Bi induced strain, effects from alloying, and defects formed during high-index (311)B crystal growth.