Phase Separation in Al x Ga1- x As Nanowhiskers Grown by the Solution−Liquid−Solid Mechanism

Low-temperature growth of Al x Ga1 - x As by the solution−liquid−solid mechanism affords nanowhiskers having two specific overall compositions: x = 0.1 and 0.8. Intermediate compositions (0.1 < x < 0.8) are inaccessible by the method employed. Examination of the nanowhiskers by transmission electron microscopy, photoluminescence spectroscopy, electron energy loss spectroscopy, and annealing studies indicates that they possess compositionally modulated nanostructures. The observed compositional modulation consists of alternating comparatively Al-rich and Ga-rich Al x Ga1 - x As domains with dimensions of 3−20 nm. The spontaneous phase separation, which occurs during growth, appears to be kinetically driven, and the resulting phase-separated nanostructures appear to be, therefore, metastable rather than stable. Spontaneous phase separation in Al x Ga1 - x As, which strongly influences its photoemission behavior, is not well understood theoretically.