Katsushi Hashio

Low dislocation density Si-doped GaAs single crystal grown by the vapor-pressure-controlled Czochralski method

Si-doped GaAs substrates have been widely used for optical devices. Recently, as the device fabrication process has changed, larger diameter substrates can be used. Almost dislocation-free Si-doped GaAs crystals of 75 mm diameter, which are suitable for the fabrication of optical devices, have been successfully grown using our vapor-pressure-controlled Czochralski (VCZ) method. The generation of slip dislocations could be suppressed and the growth of the dislocation-free crystal was achieved by decreasing the thickness of B2O3. The VCZ crystals contained a large amount of unintentionally doped boron (B) of about 1018 cm−3. By comparing the electrical data of the VCZ crystals with those of the gradient freeze (GF) crystal free from B, it is found that B acceptors decrease the intrinsic compensation ratio ([SiAs][SiGa]).

Directional solidification of InxGa1−xAs

Abstract We have investigated a constitutional supercooling and segregation phenomena in In x Ga 1− x As crystals unidirectionally solidified in a vertical system. The constitutional supercooling generates characteristic fluctuations of composition along the growth direction and this can be explained by a free nucleation ahead from the growth interface. The macroscopic compositional profiles of the grown crystals suggest that a transport of solute is mainly dominated by the diffusion. Such a growth mode is partly attributed to the difference in density between InAs and GaAs.

Development of 6-inch Fe-doped InP single crystal by vertical boat method

We have succeeded in developing 6-inch Fe doped semi-insulating InP substrates by the VB (Vertical Boat) method. To compare 6-inch substrates and commercially available 4-inch Fe-doped substrates by VB and VCZ (Vapor pressure Controlled Czochralski) methods, we measured dislocation density, X-ray topography, and electrical properties. 6-inch VB-substrates showed equivalent properties to VB substrates and much better properties than 4-inch VCZ substrates. We believe that the VB method is the most promising technology for growing 6-inch InP single crystal as well as 4-inch or smaller InP single crystals.

Growth and characterization of LEC, VCZ and VB InP single crystals

Fe-doped semi-insulating InP single crystals have been grown by LEC, VCZ and VB techniques. Dislocation density, X-ray topograph and residual strain have been measured to characterize crystallographical properties. Macroscopic and microscopic resistivity and photoluminescence intensity have been measured to estimate electrical uniformity. It was found that Fe-doped InP substrates grown by VB technique had superior properties, such as low dislocation density, no lineages and slip-lines, uniform distribution of residual strain, uniform macroscopic and microscopic distributions of resistivity and photoluminescence intensity. It is concluded that VB is the most suitable technique for the growth of high quality Fe-doped InP single crystals.