Characterization of ordered and disordered Ga 0.51In 0.49P domains by micro Raman spectroscopy

Abstract

Ga 0.51In 0.49P layers have been grown by metalorganic vapor phase epitaxy on GaAs(001) substrates misoriented 9° off towards [ 1 10] patterned on a 40 μm scale with grooves along [110]. Large (several (μm) domains of highly ordered material of the CuPt-type and of disordered zincblende-type structure coexist in the Ga 0.51In 0.49P layers as demostrated by transmission electron microscopy (TEM). Micro Raman and cathodoluminescence spectroscopy on (110) cleavage planes is applied to evaluate the impact of variation of composition and ordering effects on lattice dynamical and electronic properties with a spatial resolution of less than 1 μm. The ordered (C 3v) and disordered (T d) domains can be clearly identified from their different polarization selection rules observed in the Raman spectra. The combination of both Raman and luminescence measurements allows the determination of structure, composition (from the frequency positions of the optical phonon modes with an accuracy of 1%), and of the band gap at one location on the sample. A band gap shift of 145 meV at 5 K is measured between highly ordered and disordered domains of same composition. Furthermore, in partially ordered regions in other regions of the pattern the degree of ordering can be monitored from the transverse optical/longitudinal optical (TO/LO) intensity ratio obtained by Raman spectroscopy.