Investigation of directionally solidified InGaSb ternary alloys from Ga and Sb faces of GaSb(111) under prolonged microgravity at the International Space Station

InGaSb ternary alloys were grown from GaSb (111)A and B faces (Ga and Sb faces) under microgravity conditions on board the International Space Station by a vertical gradient freezing method. The dissolution process of the Ga and Sb faces of GaSb and orientation-dependent growth properties of InGaSb were analysed. The dissolution of GaSb(111)B was greater than that of (111)A, which was found from the remaining undissolved seed and feed crystals. The higher dissolution of the Sb face was explained based on the number of atoms at that face, and its bonding with the next atomic layer. The growth interface shape was almost flat in both cases. The indium composition in both InGaSb samples was uniform in the radial direction and it gradually decreased along the growth direction because of segregation. The growth rate of InGaSb from GaSb (111)B was found to be higher than that of GaSb (111)A because of the higher dissolution of GaSb (111)B. Engineering: A new frontier for alloys New research conducted aboard the International Space Station highlights the possibilities of materials processing in space. A team led by Yasuhiro Hayakawa at Shizuoka University in Japan sought a new way to process indium–gallium–antimonide (InGaSb) alloys, which are gaining attention as heat-to-electricity convertors and infrared sensors but can be impractically brittle when made using conventional methods. In a series of long-term crystal growth experiments performed under low-gravity conditions, Hayakawa's team was able to predictably control InGaSb composition. This is because, in outer space, GaSb starting materials dissolve at rates that depend on crystal orientations, producing concentration gradients. These gradients, in combination with favorable interfaces for uniform distributions of indium, offer ways to tune and manipulate InGaSb materials that are quite convoluted on Earth.