A New type of Graded Buffer Layer for Gas-Source Molecular Beam Epitaxial Growth of Highly Strained INxGA1−XP/GAP Multiple Quantum Wells on Gap

Abstract

ABSTRACTA new type of graded buffer layer, called graded short-period superlattice (GSSL) buffer layer, is proposed, and its effect on improving the material quality is investigated by comparing the qualities of 50-period InGaP/GaP multiple quantum wells (MQWs) grown on top of it and on a linearly graded (LG) buffer layer. Unlike the linearly graded buffer layer, in which the In composition is changed 1% per step size with a constant composition InGaP, the new buffer uses InGaP/GaP short-period superlattice within each step, while maintaining the average In composition of the short-period superlattice being changed the same amount per step size. Characterization of these structures by high-resolution X-ray diffraction and low-temperature photoluminescence indicates that, while the MQWs grown on a GSSL buffer show comparable structural properties as compared with those on an LG buffer, they exhibit higher PL intensity and narrower PL line width.