• AFM
• Hall effect
• MBE
• XRD
• metamorphic buffer
• strain
• InAs quantum wells

InAs quantum wells (QWs) are important building blocks for the realization of optoelectronic devices, spintronic applications and topological quantum computers based on Majorana fermions, due to the low electron effective mass, strong spin-orbit coupling, high g-factor, and transparent interface to superconductors. In this thesis work, InAs/InxGa1-xAs quantum wells were grown by Molecular Beam Epitaxy (MBE) on GaAs (100) substrates with optimized InxAl1-xAs step-graded metamorphic buffers. Samples were characterized by Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), High-Resolution X-Ray Diffraction (HR-XRD), and Hall measurements at low temperatures (77 K and 4 K). The growth parameters were optimized to obtain a root mean square surface roughness below 4 nm in 20×20 μm2 AFM scans. Besides, we investigated the influence of residual strain in the active region on the electrical transport properties of the InAs quantum well. We tuned the residual strain by changing the thickness of the In0.84Al0.16As overshoot layer grown on top of the step-graded buffer. We observed an increase in electron mobility with increasing overshoot thickness, achieving a peak mobility of 5.5×105 cm2/(Vs) and a carrier density of 2.4×1011 cm-2 at 4 K for a 400 nm-thick overshoot. Moreover, we studied how the quantum well thickness affects the transport properties and found that 7 nm-thick QWs have the highest mobility at 4 K, while the quality of the InAs QWs strongly deteriorates for thicknesses above 10 nm.