INTERNAL STRAIN AND DISLOCATIONS IN INXGA1-XAS CRYSTALS GROWN BY LIQUID-PHASE EPITAXY ELECTROEPITAXY

Strain relaxed, low dislocation density InxGa1-xAs crystals, 0 < x < 0 .2, have been successfully grown by Liquid phase electroepitaxy on the GaAs substrate, despite the crystal/substrate lattice mismatch. Resid ual strain in these novel substrates is below 10(-4), at least an orde r of magnitude lower than in the molecular beam epitaxially (MBE) or m etalorganic chemical vapor deposition-grown ternary buffer layers of s imilar composition. Threading dislocation density induced by both the crystal/substrate lattice mismatch and unavoidable composition variati ons has been reduced from the low 10(6) cm(-2) range, while growing di rectly on GaAs, to the mid 10(4) cm(-2) by employing both the MBE grow n ternary buffer layer and selective lateral overgrowth of an SiO2 mas k which, prior to the crystal growth, was deposited on the buffer laye r and patterned by photolithography with 10 mu m wide, oxide free seed ing windows. The full width at half maximum of the rocking curves meas ured for InxGa1-xAs crystals grown by liquid phase epitaxy/electroepit axy on patterned, closely lattice matched buffer layers was in the 20- 23 are s range. Further reduction of the dislocation density and a mor e uniform dislocation distribution is expected by modifying the initia l growth conditions, improving substrate preparation, and optimizing t he seeding window geometry.