Low etch pit density, low slip line density, and low strain indium phosphide

A method, comprising:

• sealing charge material comprising a seed crystal, an encapsulant, and a dopant in a crucible;
• sealing the crucible in an ampoule;
• performing a vertical gradient freeze crystal growth process by heating the ampoule using a multi-zone heating system to progressively melt the charge material until a portion of the seed crystal is melted;
• starting growth from the portion of the melted seed crystal by implementing a controlled cooling of the multi-zone heating system;
• applying a temperature gradient of between 1 and 8 C/cm at an interface between the melted charge material to formed crystal;
• and
• controlling a shape of the interface to be concave to the melted charge material utilizing cooling rates in the multi-zone heating system to form a solidified crystal of four inches in diameter or larger with an etch pit density of 500 cm−2 or less.