Ultra-Energy-Efficient Photoelectrode Using Microstriped GaN on Si

Abstract

A prototype photoelectrode with a unique design has been fabricated using GaN microstripes grown on a patterned Si substrate. The photoelectrode has demonstrated a record-high photocurrent density of 11 mA/cm2 upon one sun illumination and a H2 generation rate of up to 2.67 mL·cm–2·h–1. This performance with a step-change has been achieved due to the contribution from both the GaN and the silicon substrate, as such a combination covers a wide spectral region (from the ultraviolet region due to the GaN bandgap to the infrared region due to the silicon bandgap). Unlike conventional GaN grown on a silicon substrate, where a thick AlN layer is required to separate GaN from the silicon in order to avoid the well-known Ga melt-back issue, a GaN/silicon heterojunction in our photoelectrode can be formed as a result of a weak Ga melt-back reaction, which is due to the specially designed configuration of our photoelectrode grown using the microstripes. Two reference photoelectrodes have been fabricated for compari...