JAXA Japan Aerospace Exploration Agency

Development of a new crystal growth method for substrates of diode lasers

National Space Development Agency of Japan

The National Space Development Agency of Japan (NASDA) had started some of ground-based research as an initiative to space experiments in a part of the "Space Utilization Research Program" in December 1997. In the research theme of "Crystal Growth of Compound Semiconductor", long compositionally uniform single crystals of indium gallium arsenide have successfully been grown on the ground. Such single crystals had been considered so far to be grown only in microgravity.

Single crystals had been grown by a new method named the Traveling Liquidus Zone (TLZ) method which was originally invented to suppress the perturbations in the melt even in the microgravity conditions in the International Space Station (ISS). In the TLZ method, a solute-saturated melt is formed in a portion of a sample by giving an appropriate concentration gradient on the starting materials and by controlling its temperature gradient.

Space experiments are being planned using the Gradient Heating Furnace (GHF), an experiment equipment to be attached to the Japanese Experiment Module "Kibo" of the ISS. It should give more accurate and quantitative understanding of single crystal growth conditions (temperature gradient, molten zone width, etc) in the TLZ method. Based upon the acquired data, we expect to work toward practical use for the growth of large diameter uniform single crystals using the TLZ method on the ground . Besides, we plan to demonstrate the growth of single crystals up to 20mm in diameter on the ground.

Indium gallium arsenide crystal is a compound semiconductor which is very useful as a substrate of laser diodes which are used in the optical communication systems. The practical use of the crystal is expected to reduce the cost of optical communication equipment and to contribute to Information Technology (IT) infrastructure building.