Growth of InP and In1-xGaxP crystals by the vertical gradient freeze method with a submerged heater

We report the high-pressure growth of doped InP and In_1-x Ga_xP crystals by the vertical gradient-freeze method modified with the addition of a submerged heater. The submerged heater, which fits closely into the growth ampoule, effectively isolates two melt zones during growth to provide a constant doping concentration or alloy composition in the lower one, and therefore also in the crystal. The upper melt is encapsulated with B₂O₃. Since the submerged heater suppresses melt convection, it should also reduce the twinning frequency that is so troublesome for InP growth. The density of defects that result from excessive hoop stresses should also be reduced due to the essentially planar isotherm that is created near the solid-liquid interface by the submerged heater. The payoff could be a greatly improved yield of nearly unstrained InP wafers with lower defect density and more uniform electrical properties