Raman and FTIR spectroscopy of GaSb and Al_xGa_1-X alloys with nanometric thickness grown at low temperatures by liquid phase epitaxy

GaSb and Al_xGa_1-xSb thin layers were grown on (001) oriented GaSb substrates by liquid phase epitaxy technique at low temperatures. Until now, there are no previous reports on the growth of this alloy at temperatures lower than 400 °C. The layers were grown from 400 to 250 °C for the ternary layers, and at 200°C for the binary layers using a supercooling process of 10 °C and a cooling rate of 0.5 °C/min. In addition to that, ternary Al_xGa_1-xSb layers were prepared at 250 °C for several contact times 1, 5, 10, 40 and 80 minutes, and something similar was done for binary GaSb layers, with contact times of 7.5, 15, 30, 60 and 120 minutes. Infrared reflectance results show the presence of single mode spectra for GaSb layers and two mode spectra for Al _xGa_1-xSb layers corroborating the growth of the alloys, whereas Raman scattering results show also the single and two mode behaviors of the GaSb and Al_xGa_1-xSb layers respectively. In ternary layers Raman bands, such as LO-GaSb like mode undergo a shift to low energies with growth temperature and with contact time. The results suggest a greater incorporation of Al atoms in the layer for smaller contact times that with greater contact times, and also for high temperatures that with low temperatures.