Minority Carrier Lifetime Measurements by Photoinduced Carrier Microwave Absorption Method

摘要

We propose a measurement system for photoinduced minority carrier absorption of 9.35 GHz microwaves using periodically pulsed light illumination at 620 nm. The ratio of average carrier density when light illumination is ON to that when light illumination is OFF, P, was theoretically analyzed for different light pulse widths. The analysis of P resulted in a formula giving the minority carrier lifetime τ_(eff) of silicon under continuous light illumination. τ_(eff) for holes was experimentally determined using the formula, and its spatial distribution was obtained to be from 1.0 × 10~(-3) to 1.28 × 10~(-3)s for n-type silicon substrates with a thickness of 520 μm coated with 100-nm-thick thermally grown SiO_2 layers. We also demonstrated that τ_(eff) depended on the means of light illumination for a defective sample. Two different τ_(eff) values were obtained, 7 × 10~(-5) and 1.73 × 10~(-4) s, in the cases of light illumination to the top surface and rear surface, respectively, when the SiO_2 layer was etched up to 2 nm at the top surface.