Method of Cleaning Gaas Substrate, Method of Producing Gaas Substrate, Method of Fabricating Epitaxial Susbstrate, and Gaas Wafer

A method of cleaning a GaAs substrate, comprising:

• an acid cleaning step of subjecting a GaAs substrate to a plurality of acid cleanings, an acid solution for one acid cleaning of the plurality of acid cleanings being different from that for another cleaning thereof, and a total period of time for the plurality of acid cleanings being less than 30 seconds.

A method of cleaning a GaAs substrate for production of a GaAs wafer, comprising the step of:

• treating a surface of the GaAs substrate with an acid solution for less than 30 seconds.

A method of cleaning a GaAs substrate for production of a GaAs wafer, comprising the step of:

• subjecting a surface of the GaAs substrate to a plurality of treatments using a plurality of acid solutions, one acid solution in one treatment of the plurality of treatments being different from that in another treatment thereof, and a total period of time for the treatment of the GaAs substrate with the acid solutions being less than 30 seconds.

A method of cleaning a GaAs substrate for production of a GaAs wafer, comprising the step of:

• treating a GaAs substrate with an acid solution, the acid solution having a hydrogen ion concentration (pH) of not more than 6.4.

A method of cleaning a GaAs substrate for production of a GaAs wafer, comprising the step of:

• treating a GaAs substrate with an acid solution, the acid solution being a mixed solution of hydrofluoric acid and hydrogen peroxide solution, and a concentration of the hydrofluoric acid in the mixed solution being not more than 5.0 wt %.

A GaAs wafer including a cleaned primary surface, wherein the primary surface has a characteristic that a ratio of an area of a Ga (3d) peak intensity to an area of an As (3d) peak intensity in XPS evaluation is not less than 0.59.

A GaAs wafer including a cleaned primary surface, wherein the primary surface has a surface roughness of not more than 0.21 nm.

A GaAs wafer including a cleaned primary surface, wherein the primary surface has a characteristic that a ratio of an area of a Ga (3d) peak intensity to an area of an As (3d) peak intensity in an XPS spectrum is not more than 1.5.