Atomic Mechanism of Strain Alleviation and Dislocation Reduction in Highly Mismatched Remote Heteroepitaxy Using a Graphene Interlayer

Remote heteroepitaxy is known to yield semiconductorfilms withbetter quality. However, the atomic mechanisms in systems with largemismatches are still unclear. Herein, low-strain single-crystalline nitridefilmsare achieved on highly mismatched (similar to 16.3%) sapphire via graphene-assistedremote heteroepitaxy. Because of a weaker interface potential, the in-planecompressive strain at the interface releases by 30%, and dislocations areprevented. Meanwhile, the lattice distortions in the epilayer disappear when thestructure climbs over the atomic steps on substrates because graphene renders thesteps smooth. In this way, the density of edge dislocations in as-grown nitridefilms reduces to the same level as that of the screw dislocations, which is rarelyobserved in heteroepitaxy. Further, the indium composition in InxGa1-xN/GaN multiquantum wells increases to similar to 32%, enabling thefabrication of a yellow light-emitting diode. This study demonstrates the advantages of remote heteroepitaxy for bandgap tuning andopens opportunities for photoelectronic and electronic applications.