Parameters of AlGaAs epitaxial layers grown using ultrafast cooling of the growth solution

The investigation of the main parameters of the Al_xGa_1-xAs/GaAs(001) layers grown under ultrafast cooling (~10²÷10³ °C s⁻¹) of the growth solution has been carried out. Ultrafast cooling is shown to enlarge the initial solid phase composition at which the AlAs distribution over the layer thickness appears no longer monotonous. It has been found that the change of the sign of the solid phase composition gradient takes place at significantly higher temperatures compared with that for the case of equilibrium cooling as a result of the increased cooling rate. The investigation has shown high crystal quality and good PL characteristics of the grown layers. It has been found that for Al_xGa_1-xAs/GaAs structures with AlAs concentration being near the point of the direct-indirect cross-over an optical excitation at 77 K can lead to irreversible modification of PL spectra connected with the formation of the V_As-donor impurity complex.