npj Microgravity Article: Growth of InxGa1−xSb alloy semiconductor at the International Space Station (ISS) and comparison with terrestrial experiments
This article by Y Inatomi and K Sakata (apan Aerospace Exploration Agency, Sagamihara, Japan), M Arivanandhan, G Rajesh, V Nirmal Kumar, T Koyama, Y Momose and Y Hayakawa (Shizuoka University, Hamamatsu, Japan), T Ozawa (Shizuoka Institute of Science and Technology, Fukuroi, Japan) and Y Okano (Osaka University, Toyonaka, Japan) was published online on August 27, 2015.
InxGa1−xSb is an important material that has tunable properties in the infrared (IR) region and is suitable for IR-device applications. Since the quality of crystals relies on growth conditions, the growth process of alloy semiconductors can be examined better under microgravity (μG) conditions where convection is suppressed.
To investigate the dissolution and growth process of InxGa1−xSb alloy semiconductors via a sandwiched structure of GaSb(seed)/InSb/GaSb(feed) under normal and μG conditions.
InxGa1−xSb crystals were grown at the International Space Station (ISS) under μG conditions, and a similar experiment was conducted under terrestrial conditions (1G) using the vertical gradient freezing (VGF) method. The grown crystals were cut along the growth direction and its growth properties were studied. The indium composition and growth rate of grown crystals were calculated.
The shape of the growth interface was nearly flat under μG, whereas under 1G, it was highly concave with the initial seed interface being nearly flat and having facets at the peripheries. The quality of the μG crystals was better than that of the 1G samples, as the etch pit density was low in the μG sample. The growth rate was higher under μG compared with 1G. Moreover, the growth started at the peripheries under 1G, whereas it started throughout the seed interface under μG.
Kinetics played a dominant role under 1G. The suppressed convection under μG affected the dissolution and growth process of the InxGa1−xSb alloy semiconductor.
Image: Polarized optical microscope images of the etched surfaces of 1G samples