Arsenic-germanium-cadmium raw material synthesis and single crystal growth method capable of progressively improving crucible pressure difference

The invention discloses an arsenic-germanium-cadmium raw material synthesis and single crystal growth method for progressively improving crucible pressure difference. The method comprises the steps: correspondingly putting arsenic, germanium, cadmium or arsenic-germanium-cadmium raw materials into a first-layer crucible for raw material synthesis or single crystal growth; and then putting the first-layer crucible into a second-layer crucible, calculating the space volume between the first-layer crucible and the second-layer crucible, calculating according to a formula PV=nRT, and putting a proper mass of Cd elementary substance between the first-layer crucible and the second-layer crucible; and according to the same method, putting the second-layer crucible into a third-layer crucible, taking a proper amount of elemental Cd and putting into the third-layer crucible, gradually reducing the pressure difference between the crucibles, and guaranteeing experiment safety. Through the design,the pressure of the grow