Unconventional Growth Mechanism for MonolithicIntegrationofIIIVonSilicon

The heterogeneous integration of IIIV optoelectronic devices with Si electronic circuits is highly desirable because it will enable many otherwise unattainable capabilities. However, direct growth of IIIV thin film on silicon substrates has been very challenging because of large mismatches in lattice constants and thermal coefficients. Furthermore, the high epitaxial growth temperature is detrimental to transistor performance. Here, we present a detailed studies on a novel growth mode which yields a catalyst-free (Al,In)GaAs nanopillar laser on a silicon substrate by metal organic chemical vapor deposition at the low temperature of 400 C. We study the growth and misfit stress relaxation mechanism by cutting through the center of the InGaAs/GaAs nanopillars using focused ion beam and inspecting with high-resolution transmission electron microscopy. The bulk material of the nanopillar is in pure wurtzite crystal phase, despite the 6% lattice mismatch with the substrate, with all stacking disorders well confined in the bottom-most transition region and terminated horizontally. Furthermore, InGaAs was found to be in direct contact with silicon, in agreement with the observed crystal orientation alignment and good electrical conduction across the interface. This is in sharp contrast to many IIIV nanowires on silicon which are observed to stem from thin SiNx, SiO2, or SiO2/Si openings.Inaddition, GaAswasfoundtogrowperfectlyasashelllayer onIn0.2Ga0.8Aswithanextraordinarythickness,whichis 15timesgreaterthanthe theoreticalthin-filmcriticalthicknessfora1.5%latticemismatch.Thisisattributedtothecoreshellradialgeometryallowingtheouterlayerstoexpand andreleasethestrainduetolatticemismatch.The findingsinthisstudyredefinetherulesforlattice-mismatchedgrowthonheterogeneoussubstratesand device structure design.