Liquid Encapsulated Czochralski Growth of GaAs

Abstract

Melt growth of gallium arsenide single crystals by the Czochralski technique has required rather complex equipment because of the high vapor pressure of arsenic. A recently developed technique known as liquid encapsulated growth overcomes a number of the problems involved and allows gallium arsenide to be grown in a commercial silicon crystal puller. Crystals about 1 in. in diameter weighing 80g have been grown nearly routinely. One crystal with a maximum diameter of 21/4 in. weighing 370g was grown, but it appears to be highly strained. Undoped crystals grown in quartz or alumina crucibles have as‐grown resistivities greater than 105 ohm‐cm. On heat treatment at 800°C for 24 hr, the crystals grown in quartz convert to n‐type with carrier concentrations in the range 1015 cm−3 to 1016 cm−3 and room temperature mobilities from 5400 cm2V‐sec to 6300 cm2/V‐sec. The crystals grown in alumina retain high resistivity after heat treatment. The heat treatment behavior is explained by a model based on the incorporation of molecules in the crystals grown in quartz and the breakup of these molecules into silicon atoms and molecules on heat‐treatment.