Scale up of In_xGa_<1-x>A_s (x: 0.08 - 0.13) Platy Crystals for Semiconductor Laser Substrates

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In_xGa_<1-x>A_s (x: 0.1 - 0.2) single crystals are promising as substrates of laser diodes for wavelength of 1.3 μm used in the optical communication system. However, the growth of such ternary bulk single crystals with uniform composition is not easy and high quality substrates have not been prepared before we succeeded in growing InxGa1-xAs (x: 0.1 - 0.13) platy crystals by the TLZ method. The TLZ method, which we originally invented for homogeneous alloy crystal growth in microgravity [1-3], requires diffusion limited mass transport and convection in a melt should be avoided. In order to fulfill both requirements of large surface area for substrates and suppression of convection during crystal growth, we grew platy crystals instead of large diameter cylindrical crystals. Convection in a melt was sufficiently suppressed by limiting the thickness of platy crystals to 2 mm. As a result, homogeneous In_xGa_<1-x>A_s (x: 0.08 - 0.13) single crystals with high quality surface area of larger than 10×10mm^2 were grown. For substrate use, larger area is required and mass productivity is also required. This year, we studied scale up of platy crystals in preparation for commercialization of laser diodes as well as improvement of crystal quality. Here, we report on the results obtained this year.
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