Self-Organized Dot/Columnar Structures and Quasi-Perfect CuPt-Type Ordering in (GaP)n(InP)n Superlattices Grown on GaAs (N11) Substrates by Gas Source Molecular Beam Epitaxy

Abstract

(GaP)n (InP)n short-period superlattices (SLs) are grown on GaAs (N11) and (100) substrates by gas source molecular beam epitaxy. Transmission electron microscopy observations show that the SLs grown on GaAs (311)A and (411)A have lateral-composition-modulated dot/columnar structures with a lateral period of about 10–20 nm, while on GaAs (100), wire structures are formed. Photoluminescence (PL) peak energies are greatly dependent on substrate orientation and monolayer number n corresponding to the lateral composition modulation. On the other hand, the (GaP)n (InP)n SLs grown on GaAs (111) have no lateral composition modulation for n≤4 and have quasi-perfect CuPt-type ordering along the <111> growth direction for n=1, where the PL peak energy is 321 meV lower than that of disordered InGaP alloy. Quantum dots formed in (GaP)2(InP)2.5 SL/ In0.49Ga0.51P multilayers by self-organization exhibit strong 77 K PL with a full width at half-maximum of about 70 meV. Anomalous temperature variation of PL peak energy is observed in these self-organized structures.