Kouichi Sogabe

Morphology and X-Ray Diffraction Peak Widths of Aluminum Nitride Single Crystals Prepared by the Sublimation Method

AlN single crystal is one of the promising materials for substrates of GaN-based laser diodes. We prepared aluminum nitride single crystals by the sublimation method and characterized them. The crystals are transparent and slightly yellow. Some crystals are needle-shaped with a hexagonal cross section, diameter of 0.5 mm and length of 3 mm, grown parallel to |001|. Other crystals are plate-shaped with a maximum width of 3 mm, 5 mm length and 0.5 mm thickness, grown with a large (001) face. Also, other crystals are needle-shaped with a rectangular cross section, width of 1 mm, 7 mm length and 0.3 mm thickness, grown with a large (101) face. Their widths of X-ray rocking curves is about 39 arcsec, with a full width at half-maximum, 203 arcsec and 12 arcsec, respectively. The orientation of AlN single crystal axis is sufficient for use in substrates for GaN-based diodes.

One role of titanium compound particles in aluminium nitride sintered body

Microstructure of titanium compound particle in polycrystalline aluminium nitride (AlN) has been investigated using micro-auger electron spectroscopy (μ-AES). AlN-0.5 wt% TiO2-1.5 wt% Y2O3-0.4 wt% CaO system was sintered at 1850°C in nitrogen atmosphere using a graphite furnace. The AES studies show that the composition of the titanium compound particle is titanium, aluminium, carbon, oxygen, nitrogen and calcium. On the other hand, no calcium is observed by AES in the AlN grains and grain boundary. It is found that one role of the titanium compound particle is to trap calcium included in polycrystalline AlN.

Determination of the range of lattice distortion in AIN sintered body by higher order laue zone pattern

To analyse the magnitude and range of lattice distortion which is responsible for the low thermal conductivity in aluminium nitride (AIN) crystal grains, the higher order laue zone (HOLZ) pattern of transmission electron microscopy was used. The HOLZ patterns obtained from various positions in the AIN crystal grain show that the AIN crystal lattice is distorted in the vicinity of the grain-boundary phase, and the magnitude of lattice distortion becomes large as it approaches the grain-boundary phase. Also, the range of distortion extends to approximately 300 nm from the grain-boundary phase.