Optimization of MBE Growth Conditions of In0.52Al0.48As Waveguide Layers for InGaAs/InAlAs/InP Quantum Cascade Lasers

Abstract

We investigate molecular beam epitaxy growth conditions of micrometers-thick In0.52Al0.48As designed for waveguide of InGaAs/InAlAs/InP quantum cascade lasers. Effect of growth temperature and V/III ratio on the surface morphology and defect structure were studied. The growth conditions which were developed for the growth of cascaded In0.53Ga0.47As/In0.52Al0.48As active region, e.g. growth temperature of TG=520°C and V/III ratio of 12, turned out to be not optimum for the growth of thick In0.52Al0.48As waveguide layers. It has been observed that after exceeding ~1µm thickness the quality of In0.52Al0.48As layers deteriorates. The in-situ optical reflectometry showed increasing surface roughness caused by defect forming, which was further confirmed by High Resolution X-Ray reciprocal space mapping, optical microscopy and atomic force microscopy. The presented optimization of growth conditions of In0.52Al0.48As waveguide layer led to the growth of defect free material, with good optical quality. This has been achieved by decreasing the growth temperature to TG=480 °C with appropriate increasing V/III ratio. At the same time the growth conditions of the cascade active region of the laser were left unchanged. The lasers grown using new recipe have shown lower threshold currents and improved slope efficiency. We relate this performance improvement to reduction of the electron scattering on the interface roughness and decreased waveguide absorption losses.

Special Issue “Advances in Epitaxial Materials”-Editorial Preface

“…The second epitaxial method used mostly in academic labs is molecular beam epitaxy (MBE). This method was also used in four papers [ 2 , 5 , 6 , 7 ]. Such a balance between the number of papers on MOVPE and MBE reflects the interests of scientists.…”

“…Two papers describe the growth and properties of more classical III-V epitaxial layers: GaInAsSb on GaAs [ 6 ] and InAlAs/InGaAs/InP [ 7 ]. These semiconductors are used in manufacturing high-mobility transistors, photovoltaic cells, and infrared/red light emitters, as well as novel devices as cascade lasers.…”