METHOD OF MAKING QUANTUM WELL STRUCTURE WITH HIGHLY MISMATCHING LATTICE

摘要

PURPOSE: To obtain a quantum well structure having highly incommensurate lattice by forming a strain free barrier layer and a quantum well structure on an effective substrate provided with a buffer layer and a super lattice structure thereby spatially separating strain in the quantum well structure. CONSTITUTION: A quantum well structure 5 is constituted by growing multiple semiconductor layers sequentially on a substrate 10. At first, a buffer layer 20 of semiconductor material thicker than a critical thickness is grown on the substrate 10 while having lattice incommensurate to that of the substrate 10. A strained superlattice structure 30 is then grown on the buffer layer 20 to obtain an effective substrate 10-20-30 having a modified lattice constant. Subsequently, a quantum well active region 40-50-60 is formed. Incommensurateness of lattice constant between a quantum well layer 50 and a barrier layer 40 is smaller than that between the quantum well layer 50 and the substrate 10. Thereafter, a second superlattice structure 70 is grown on a barrier layer 60 and a cap layer 80 is grown thereon.