Optical evaluation of carrier lifetime and diffusion length in synthetic diamonds

The key electronic parameters of high-pressure-high-temperature and chemical-vapor-deposition grown diamonds have been determined at interband (hv=5.82 eV) or below bandgap (hv=4.68 eV) photoexcitation, using a picosecond transient grating (TG) technique. TG kinetics directly provided the values of ambipolar diffusion coefficient (6-10 cm(2)/s) and carrier lifetime (in a range from 0.17 to 2.8 ns) for crystals grown under different conditions. The carrier diffusion length was found to vary from 0.5 mu m in CVD layers to 1.6 mu m for IIa type HPHT diamond crystal. The carrier lifetimes correlated well with the nitrogen-related defect density in both types of diamonds. (C) 2008 Elsevier B.V. All rights reserved.