Gallium Phosphide nanostructure on Silicon by Silica nanospheres lithography and Metal Assisted Chemical Etching

Abstract

This work focuses on exploring the ways to integrate III-V nanostructures on silicon to enhance the current silicon cell's efficiency by effective absorption and possibly using quantum mechanical phenomena such as MEG (multiple exciton generation) and effective absorption of light above the band gap in the nanostructures' confined states. The gallium phosphide (GaP) is integrated with silicon wafers in the form of nanostructures. GaP is epitaxially grown on silicon, and the nanostructures are fabricated by silica nanospheres lithography (SNL) with metal assisted chemical etching (MACE). With optimized MACE condition, we are able to fabricate these nanopillars on GaP with controlled size and aspect ratios. Silica nanospheres are coated on the GaP is on Si by spin-coating, and their size is modified by a reactive ion etching (RIE) process. Palladium (Pd) is deposited on the sample by electron beam deposition for MACE process. In this MACE process, we control the MACE solution by changing the ration of HF and H2O2 concentrations. The GaP nanostructures created from MACE solutions with high HF and H2O2 concentrations is taller and possesses a more well-defined shape. Also, GaP nanostructures created from different metal of MACE such as Pd, Au and Ti/Au. MACE with Pd shows the better shape nanostructure than others.