Investigating non-equilibrium carrier lifetimes in nitrogen-doped and boron-doped single crystal HPHT diamonds with an optical method

Non-equilibrium carrier lifetimes in nitrogen-doped and boron-doped single crystal HPHT diamonds have been investigated using a non-destructive optical method. In this method, a fiber was used to send a probe beam into the double-side polished sample and collect the interference beams reflected from the front and rear surfaces for directly measuring the refractive index change with a spatial resolution of about 10 μm. Carrier lifetimes at several points in each sample have been investigated, whose relationships with the impurity concentrations have been analyzed. The nitrogen impurity can effectively reduce the carrier lifetime. Fast and slow carrier recombination components have been found in the boron-doped sample, which are caused by the deep traps and the compensated boron impurity, respectively. This investigation method can also provide a scheme for estimating the impurity concentration in diamond with a high spatial resolution.