Method for passivating surface of InGaAs device with composite film

The invention provides a method for passivating the surface of an InGaAs device with a composite film. The method comprises the following steps: covering the surface of the InGaAs device with a sulfur atom layer, and covering the sulfur atom layer with a layer of silicon nitride or silicon oxide dielectric film, wherein the sulfur atom layer is formed by an anodic sulfurization method. According to the method, sulfur atoms are combined with dangling bonds on the surface of the InGaAs device during an electrochemical reaction process to close an electronic channel generated by the dangling bonds and isolate an electron-hole surface recombination mechanism on the surface of the InGaAs device; and the method has the advantages of simplicity in operation and low cost.