Application Raman scattering studies of strain effects in (100) and (311)B GaAs12xBix (original) (raw)

We report room-temperature Raman studies of strained (100) and (311)B GaAs1xBix epitaxial layers for x0.039. 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(C) mode experiences a strong composition-dependent redshift as a result of alloying. The peak frequency decreases linearly from the value for pure GaAs (293 cm1) with the alloyed Bi fraction x and the introduced in-plane lattice strain ek, by DxLO ¼ Dxalloy  Dxstrain. X-ray diffraction measurements are used to determine x and ek allowing Dxalloy to be decoupled and is estimated to be 12(64) cm1/x for (100) GaAs1xBix. DxLO 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.