Microstructural and optical properties of InGaAs/InAlAs multi quantum well structures grown by molecular beam epitaxy method with post-an[n]ealing process

Abstract

We investigated the annealing effects on In0.53 Ga0.47As/In0.52Al0.48As multi quantum wells using RTA, and following optical, structural and compositional properties. In this research, We used GaAs(100) substrate with metamorphic buffer layer to maintain the quantum wells lattice parameter and InP(100) substrate which was same lattice parameter of it. It was grown by Molecular Beam Epitaxy (MBE), annealed from $650^\circ C$ to $800^\circ C$ per $50^\circ C$ for 30 sec and additionally $900^\circ C$ using Rapid Thermal Annealing (RTA). For Analyzing of thermal effects, we investigated Photoluminescence for optical analysis and, using Atomic Force Microscopy (AFM), High Resolution XRD (HRXRD), Auger Electron Spectroscopy (AES), and High Resolution Transmission Electron Microscopy (HRTEM), observed structural feature and change. All of samples showed blue shift with increasing annealing temperature. In GaAs(100) case, blue shift was 49.8 meV and InP(100) case was 4 meV. Especially, PL intensity was higher in GaAs(100) cases than InP(100) cases. Surface morphology observed by AFM showed few nm size hole and hillock which was created by residual $As_2$ gas and related with removing of top $SiO_2$ capping layer. HRXRD showed that multi quantum wells on GaAs(100) had residual stress which transformed its lattice parameter about 2%, but others on InP(100) were not. This residual stress much effect on multi quantum wells properties, such as well roughness, band gap, intermixing process, etc. In HRTEM images showed that multi quantum wells on GaAs(100) had rough boundaries. As annealing process was progressed, multi quantum wells are mainly unevenly degraded and intermixed between quantum well and barrier. Although degradation was main phenomenon, we could know that the degradation was not simply degradation, because, when it was annealed at $700^\circ C$, it showed the very clear boundaries. On the contrary, multi quantum wells on InP(100) had much little residual...