Direct Growth of a GaInP/GaAs/Si Triple-Junction Solar Cell:The horizontal Bridgman method and its various improved models account for more than half of the GaAs growth market.
In most cases, the ampoule includes an independent chamber containing solid arsenic, which leads to the main chamber through a limited aperture. This arsenic containing chamber can provide the arsenic overpressure required to maintain the chemical ratio. The ampoule is placed in a SiC furnace tube, which is placed on a semicircular, usually SiC groove. Then the heating furnace body of the furnace tube moves and starts the growth process through the filler. This reverse movement is usually adopted instead of moving the filler through the furnace body in order to reduce the disturbance to the crystal. The furnace temperature is set so that the filler can be completely melted when it is completely out of the furnace body. In this way, when the furnace body moves over the ampoule, the molten GaAs filler at the bottom of the ampoule recrystallizes to form a unique "d" "Shaped crystal. If desired, the seed crystal can also be placed in contact with the melt. The crystal diameter grown by this method is generally 1-2in. To grow larger crystals, it is necessary to accurately control the chemical composition in the axial direction, while in the radial direction, it is necessary to accurately control the temperature gradient to obtain the low dislocation density. The Bridgman method is characterized by the use of ampoules to hold the melt, which allows Crystal growth was carried out under a small thermal gradient to obtain a wafer with defect density less than 10 ^ 3cm ^ - 2
Vertical Bridgman method (VB method and crucible descent method) can be said to be a new method for growing GaAs single crystals. It combines the advantages of horizontal Brinell method and liquid sealed Czochralski method, and can directly grow circular GaAs single crystals with good integrity; And vertical gradient solidification method (VGF method). In addition, the process simulation of GaAs is realized by establishing a computer model, including femag / DS and femag / VB of directional solidification method (DS method), VB method and VGF method.