Molecular beam epitaxy of Al0.48In0.52AsGa0.47In0.53As heterostructures on metamorphic AlxGayIn1 − x − yAs buffer layers

Abstract Ternary Al x In 1 − x As Ga y In 1 − y As heterostructures with a lattice mismatch up to 4% are grown on GaAs by molecular beam epitaxy. Two buffer layer concepts to compensate the lattice misfit between the Al x In 1 − x As Ga y In 1 − y As layers and the GaAs substrate using the quaternary Al x Ga y In 1 − y As in a linear graded and two-step graded fashion, respectively, are presented. The Al and Ga content of the ternary layers were chosen to be x = 0.48 and y = 0.47, respectively, in order to obtain the same heterostructures identical to those grown lattice matched on InP as a reference. The surface morphology and the transport properties of Al 0.48 In 0.52 As Ga 0.47 In 0.53 As high-electron mobility transistor structures were studied by atomic force microscopy and Hall measurements, respectively. Optical properties were investigated by low-temperature photoluminescence on quantum well structures. The use of the two step graded buffer layers resulted in three-dimensional layer growth and inferior layer quality. In contrast, the linear graded buffer approach was found to result in superior heterostructure properties due to the two-dimensional growth mode during the whole growth process resulting in the typical cross-hatched surface morphology.