Spatially resolved cathodoluminescence spectroscopy of InGaN/GaN heterostructures on m-plane GaN grown on patterned Si (112) substrates

The optical properties of GaN/InGaN heterostructures grown by MOVPE on pre-patterned Si substrate have been studied using cathodoluminescence (CL) at low temperatures (T=5.4 K). A stripe mask pattern was produced on the Si (112) substrate using photolithography and ICP-RIE. Anisotropic wet etching resulted in (-1-11) Si sidewalls and (112) Si terraces connected by (111) Si facets. After the growth of an AlN layer the (111) and (112) Si facets were masked with SiO2. The lateral and vertical epitaxial growth of GaN was initiated at the (-1-11) Si sidewalls resulting in a partially coalesced m-plane surface. Finally, an InGaN layer capped with p-GaN was deposited. The GaN (D0,X) emission observed from the +c-wing is red-shifted possibly due to tensile strain and the incorporation of impurities. Homogeneous and intense CL from InGaN is emitted from nearly the entire m-plane surface at about 3.2 eV with a FWHM of 98 meV. Just above the -c-wing the CL intensity from InGaN is reduced due to the presence of stacking faults and defects. The influence of BSFs on lifetimes of (D0,X) and InGaN emissions will be discussed.