Indium adatom migration during molecular beam epitaxial growth of strained InGaAs/GaAs single quantum wells

Abstract

Indium composition variations in strained InGaAs/GaAs quantum wells grown on nonplanar substrates by molecular beam epitaxy have been analyzed by spatially and spectrally resolved low-temperature cathodoluminescence. For our growth conditions, the In adatom migration length on (100) facets has been determined to be ∼25 μm. A maximum relative increase of In incorporation of ≅6% on (100) ridges is observed and is found to be strain independent (In composition) for quantum wells nominally 35 and 70 Å thick with In composition of 0.10-0.22. Significantly asymmetric indium adatom migration is observed between adjacent (100) facets for ridges and grooves formed with (111)A and (311)A multifaceted sidewalls, indicating that multifaceting kinetically inhibits adatom migration. For structures designed for one-step growth of index-guided injection lasers with built-in nonabsorbing waveguides, we show that differences greater than 80 meV in the effective band gap of a 70 Å quantum well can be achieved between the gain region and the nonabsorbing waveguide without relaxing the strain.