Photocarrier radiometry of ion-implanted and thermally annealed silicon wafers with multiple-wavelength excitations

Abstract

The electronic transport properties of ion-implanted and thermally annealed silicon wafers and their effects on the room temperature photoluminescence have been investigated by a two-layer photocarrier radiometry (PCR) model with multiple-wavelength excitations. Simulations are carried out to show the dependences of the PCR amplitudes on the structural and transport properties (thickness, minority carrier lifetime, diffusion coefficient, and front surface recombination velocity) of the implanted layer with excitation in a wide spectral range, respectively. Experiments on As+ implanted and thermally annealed silicon wafers with ion fluences ranging from 5 × 1014 to 1 × 1016 cm−2 were performed, with 830 nm, 660 nm, and 405 nm excitations. Both the simulated and experimental results show that the transport properties of the implanted layer can be obtained by fitting the PCR amplitudes under the multi-wavelength excitations at a fixed modulation frequency to the theoretical model via a multi-parameter fitting procedure. The ion implantation and thermal annealing processes result in significant decreases of the minority carrier lifetime and diffusion coefficient of the implanted layer, and the recombination velocity at the front surface, and all three parameters decrease with the increasing ion fluence. The photoluminescence of the ion-implanted and thermally annealed wafers is significantly stronger than that of the non-implanted and non-annealed wafer, mainly due to the considerable decline of the front surface recombination velocity. In addition, the decreasing carrier diffusion coefficient of the implanted layer may be another reason for the enhancement of the photoluminescence under long-wavelength excitations.