Liquid-encapsulated Czochralski growth of Ga_(1-x)In_xAs single crystals with uniform compositions

摘要

Most alloy semiconductors tend to develop severe macrosegregation along single crystals grown from melts. The feasibility of modifying the conventional liquid-encapsulated Czochralski (LEC) process to reduce macrosegregation was assessed. First, the crystal was pulled from the melt in a stationary inner crucible that was replenished by the melt overflowing from a rising outer crucible. Ga_(1-x)In_xAs single crystals of about 1, 2 and 3mol% InAs were grown. When growing crystals at higher InAs contents, the replenishing melt had a tendency to freeze and disrupt crystal growth. The crystal was then pulled from a melt which was replenished from below by a solid feed held in the same rising crucible as the melt. The solid feed was prepared from a B_2O_3-encapsulated melt that undercooled and then rapidly solidified into an ingot without macrosegregation. Ga_(1-x)In_xAs single crystals of about 5 and 7.5mol% InAs were grown. All crystals were uniform in composition in both the axial and the radial directions. It was also demonstrated that the first modified LEC process can be used to grow inhomogeneous Ga_(1-x)In_x As single crystals from pure GaAs seeds and initially pure GaAs melts, which is convenient when no alloy crystal seeds are available.