The importance of lattice mismatch in the growth of GaxIn1−xP epitaxial crystals

Abstract

The importance of lattice-parameter mismatch between the GaAs substrate and the GaxIn1−xP epitaxial layer on crystal growth and properties has been investigated. Three major effects were observed: (i) The crystal morphology and substrate/epitaxial-layer interface were found to be nearly perfect for a0 ≈ a0 GaAs and very poor including melt inclusions at the interface for other epitaxial-layer compositions. (ii) The dislocation density was found to depend on a0 - a0 GaAs varying from 105 to > 108 cm−2. (iii) The excess energy due to lattice-parameter mismatch was found to perturb the solid composition from the chemical-equilibrium composition toward the composition which minimizes mismatch; i.e., epitaxial layers with x=0.51±0.01 are grown from Ga–In–P liquids with chemical-equilibrium solidus compositions ranging from 0.46 to 0.62. The result is that under the growth conditions used, highly perfect epitaxial layers could be grown only near x=0.51 with band gaps near 1.9 eV. Other compositions with EG>1.9 eV were highly imperfect with poor morphology, melt inclusions, and large numbers of dislocations.