| 摘要 |
An apparatus (230) for measuring the minority carrier lifetime of a semiconductor sample (232) using radio-frequency coupling. The measuring apparatus (230) includes an antenna (244) that is positioned a coupling distance from a semiconductor sample (232) which is exposed to light (236) pulses from a laser (234) during sampling operations. A signal generator (240) is included to generate high frequency, such as 900 MHz or higher, sinusoidal waveform signals that are split into a reference signal and a sample signal. The sample signal is transmitted into a sample branch circuit where it passes through a tuning capacitor (260) and a coaxial cable (262) prior to reaching the antenna (244). The antenna (244) is radio-frequency coupled with the adjacent sample and transmits the sample signal, or electromagnetic radiation corresponding to the sample signal, to the sample and receives reflected power or a sample-coupled-photoconductivity signal back. To lower impedance and speed system response, the impedance is controlled by limiting impedance in the coaxial cable (262) and the antenna (244) reactance. In one embodiment, the antenna 244 is a waveguide/aperture hybrid antenna (244) having a central transmission line (286) and an adjacent ground flange. The sample-coupled-photoconductivity signal is then transmitted to a mixer (270) which also receives the reference signal. To enhance the sensitivity of the measuring apparatus (230), the mixer (270) is operated to phase match the reference signal and the sample-coupled-photoconductivity signal. |
