Gallium arsenide single crystal substrate, method of producing gallium arsenide single crystal, and method of producing gallium arsenide single crystal substrate

A method of producing a gallium arsenide single crystal having electron-donating type conductivity using a vertical boat method, the method of producing the gallium arsenide single crystal comprising:

• preparing a single crystal growth apparatus at least including a crucible having a cylindrical shape and a heating apparatus disposed to surround an outer periphery of the crucible;
• accommodating a seed crystal at a bottom portion of the crucible and accommodating an electron-donating type dopant, boron oxide, metal arsenic, and a gallium arsenide polycrystal in a form of a bulk or powder above the seed crystal in the crucible, the seed crystal being composed of the gallium arsenide single crystal;
• heating the crucible using the heating apparatus to sublimate the metal arsenic, melt the boron oxide into a boron oxide melt, melt a part of the seed crystal and the gallium arsenide polycrystal into a gallium arsenide melt, obtain a first melt in which the electron-donating type dopant is dissolved in the gallium arsenide melt, and bring the first melt into contact with a remainder of the seed crystal;
• and
• obtaining the gallium arsenide single crystal by growing a crystal from the first melt on the remainder of the seed crystal, wherein
• the single crystal growth apparatus includes a branch pipe portion that controls a partial pressure of arsenic in the crucible,
• in the obtaining the gallium arsenide single crystal, an end surface of the first melt not in contact with the remainder of the seed crystal is covered with the boron oxide melt by 10 area % or more and 50 area % or less, and
• in the obtaining the gallium arsenide single crystal, the gallium arsenide in the first melt has an atomic ratio of arsenic to gallium greater than 1.