Synthesis of AlGaN and InN crystals under high pressures

Saito, Hiroyuki; Utsumi, Wataru; Kaneko, Hiroshi*; Aoki, Katsutoshi

We have performed synthesis studies of various III-V nitrides crystals, key materials for optoelectronic and high-power/frequency devices, using a cubic-anvil-type large volume high-pressure apparatus combined with in situ X-ray diffraction. Polly-crystallines of AlGaN alloys covering a composition range of 0 x 1 were synthesized by a solid-phase reaction under high pressure. In situ X-ray diffraction profiles were measured to observe the alloying process, which started at around 800C under 6.0 GPa. Single crystal of AlGaN was also successfully obtained by slow cooling of its melt from 2400C at 6.5 GPa. For InN, its phase diagram was determined under high P-T conditions up to 20GPa and 2000C based on the in situ observations, which demonstrates that 19GPa and 1900C are needed for its congruent melting.