No abstract

GaSe crystals were doped with indium, and improvements in the mechanical properties and second-harmonic efficiency over pure crystals were obtained. Both effects are due to an improvement in the crystal quality of the material, and it was shown that doping with low levels of indium did not alter the intrinsic value of the nonlinear d coefficient.

The physical vapor transport technique can be employed to fabricate large diameter silicon carbide crystals (up to 50 mm diameter) exhibiting uniform 4H‐polytype over the full crystal volume. Crystal growth rate is controlled to first order by temperature conditions and ambient pressure. 4H‐polytype uniformity is controlled by polarity of the seed crystal and the growth temperature. 4H‐SiC crystals exhibit crystalline defects mainly in the form of dislocations with densities in the 104 cm—2 range and micropipe defects, the latter having densities as low as 10 cm—2 in best crystals. Electrical conductivity in 4H‐SiC bulk crystals ranges from <10—2 Ω cm, n‐type, to insulating (>1015 Ω cm) at room temperature.