Site-controlled growth of InP/GaInP islands on periodic hole patterns in GaAs substrates produced by microsphere photolithography

Abstract

We present microsphere photolithography in combination with wet chemical etching as a fast and low-cost method to produce regular hole arrays in a (100) GaAs surface, which are suitable for controlled nucleation of self-organized InP islands in a metal–organic vapor-phase epitaxy (MOVPE) system. A hexagonal close-packed monolayer of microspheres is used as an array of microlenses to focus UV-light on UV-sensitive photoresist. In this way, regular arrays of holes with 2μm spacing can be realized in the photoresist with controllable feature size in the sub-μm range, which are transferred to a GaAs buffer, using an isotropic etchant. These templates are used to study the site-controlled nucleation of InP islands on a Ga0.51In0.49P barrier. For this purpose the subsequent overgrowth of the templates with a GaAs buffer layer and the GaInP barrier is investigated previous to the additional deposition of the InP. The template quality is monitored during structuring and overgrowth experiments using atomic force microscopy (AFM). Preferred nucleation of InP islands inside the almost filled holes can be observed for uncapped samples. The correlation between the initial patterning and the optical signal of the InP islands is investigated by micro-photoluminescence (micro-PL) measurements. We observe site-controlled nucleation of large, but optically active, InP islands on these templates.