Redistribution of impurities in graded-gap layers of AlGalnAsP(InAs) in the process of zone recrystallization

The liquid-phase gradient epitaxy method was used to obtain Al^Ga^Inj _ AszPj _z layers doped with tellurium with thicknesses of 500-1000 pm at synthesis temperatures of 800-900 °C. The Hall coefficients were determined by etching the surface of graded-gap layers at a weak magnetic field with a strength of H— 2.4 • 105 A/m. The dependence of the distribution of the content of the majority charge carriers over the thickness of the layers was calculated and plotted using the Runge-Kutta method. When the undoped liquid zone of A1 - Ga - As - P - In moves in the forward direction, its source is InAs : Те, and when the solution-melt doped with tellurium moves in the opposite direction, the source is the graded-gap crystal of AlGalnAsP. For this reason, as well as because of the high value of the tellurium diffusion coefficient, after passing the zone in the opposite direction, there is no equalization of the Те impurity content in the layer. Due to the high diffusion coefficient of aluminum and phosphorus, the features of the redistribution of these components in the graded-gap layers of AlGalnPAs grown on InAs substrates are discussed. The high concentration of A1 and P atoms in the layers adjacent to the heterointerface, the diffusion of Te from InAs into the layer during the growth of the heterostructure contribute to a higher cleaning depth of the AlGalnPAs layer from tellurium impurities in comparison with the layers of the substrate material. A decrease in the concentration of the majority charge carriers in the layer near the substrate is probably due to structural defects at the layer-substrate boundary.