Raman Scattering Study of InxGa1-xN Alloys with Low Indium Compositions.

In_xGa_1-xN alloys with low indium composition x in the range 0.13 ≤ x ≤ 0.23 are systematically studied mainly based on a Raman scattering technique. Scanning electron microscopy and x-ray diffraction results show that our samples can be divided into two groups: pseudomorphic (0.13 ≤ x ≤ 0.16) and relaxed (0.18 ≤ x ≤ 0.23). The prominent enhancement of A₁ longitudinal-optical (LO) mode is found with 325nm laser excitation. For pseudomorphic samples, the frequencies of A₁ (LO) phonons agree well with the theoretical predictions, which verifies that the samples are fully strained. For relaxed In_xGa_1-xN samples, a linear dependence of the A₁ (LO) mode frequency is obtained: Ω0(x) = (740.8 ± 3.3) -- (143.1 ± 16.0)x, which is the evidence of one-mode behavior in In_xGa_1-xN ternary alloys. Residual strains in these partially relaxed samples are also evaluated. [ABSTRACT FROM AUTHOR]