Conductivity and photoconductivity in boron doped diamond films: Microwavemeasurements

We used the microwave technique to measure electrical properties of heavily boron doped diamond films. This technique overcomes problems such as the p resence of parasitic resistance due to the electrical contacts. The conduct ivity of these films is rather high (about 10(4) S m(-1)). The measured mic rowave conductivity has the same values as the dc conductivity. The conduct ivity varies with the doping. The highest value of conductivity does not ap pear for the highest value of doping, because of the presence of a parasiti c phase. This will be proved by electron spin resonance and Raman spectra. Theoretical calculation rules out the skin effect in our measurements. It w ill be also possible to perform microwave photoconductivity measurements. T he photoconductivity behavior varies in the opposite way to the conductivit y. One explanation, based on the recombination time which decreases with th e conductivity, will be presented. (C) 2001 American Institute of Physics.