Optimize wet etch method for high yield AlAsSb/InGaAs avalanche photodiode fabrication

Abstract The AlAsSb avalanche photodiode (APD) is a type of excellent high-sensitivity infrared detectors with low excess noise, owing to the intrinsic low β to α ratio of AlAsSb. This material overcomes the challenge of achieving low noise performance in conventional InP-based infrared APDs. However, from a fabrication perspective, AlAsSb gets oxidized rapidly during the etching process, which significantly hinders device properties, therefore, reduces device yield. In this work, we optimize a wet etching method utilizing a mixture of H 2 SO 4 :H 2 O 2 : H 2 O for etching non-Sb contained layers, followed by a mixture of HCl: H 2 O 2 : H 2 O for etching Sb-contained layers. A summary of etching rates for different etching solution combinations is illustrated. Here firstly proposes to deploy an oxidization induced color changing as an indicator to swap etching solution. This method has been examined and supported by energy dispersive x-ray (EDX) results and scanning electron microscope images. A comparison between two APDs with and without residues confirms that the dark current of the APD is reduced two orders of magnitude with clean surface.