Three samples with different doping levels were prepared for the experiment. The sample cube was put in a graphite crucible. Three crucibles were sealed in a quartz ampoule in a high vacuum with quartz wool that absorbed shock during launch. Then the ampoule was put in a graphite block and was sealed in a Ta cartridge. The sample was heated up to 850degC to dissolve the inner surfaces of the GaAs substrates, and to form a Ga-As solution.
Dissolution stops when the solution was saturated with As.
In contrast, there is no apparent difference in growth thickness among the six substrates placed in a sample cube. From a macroscopic view, the effect of the convection-free condition on the dopant atom distribution along the growth direction is thus not seen. In contrast, for the 1-g grown crystal, type II striations developed toward the growth direction and passed through the whole grown layer. As the result, many macrosteps remained at the crystal surface.