OVERCOMING THE PSEUDOMORPHIC CRITICAL THICKNESS LIMIT USING COMPLIANT SUBSTRATES

We demonstrated the high-quality molecular beam epitaxy growth of exceedingly thick In0.14Ga0.86As pseudomorphic layers on thin, free-standing, compliant GaAs substrates. We first fabricated 800-angstrom-thick compliant platforms before growing a lattice-mismatched layer on the platform. The layer we grew exceeds its usual critical thickness by about twenty times without strain relaxation. X-ray analysis confirms a shift in the InGaAs peaks grown on the compliant substrate, indicating an unrelaxed strain of 0.9%. Moreover, atomic force microscope profiles verify that layers grown on compliant substrates are much smoother than layers grown on a plain substrate.