Carrier dynamics in CVD diamond: electron and hole contributions

摘要

The transport properties in synthetic diamond are studied using high quality diamond films grown by microwave plasma enhanced chemical vapor deposition (CVD). In particular, electron and hole contributions to the diamond carrier dynamics are successfully separated and defect distribution inside specimens is obtained. This is achieved through a systematic investigation of the signals obtained from properly biases diamonds irradiated with differently penetrating nuclear particle.s To this purpose ~(12)C ions produced by the 15 MV Tandem accelerator of the Southern National Laboratories of INFN in Catania (Italy) are used as a probe. The ion beam energy is varied in the 22-91 MeV range (penetration depth from 10.6 mum to the thickness of the used samples, deposited energies from 22 to 62 MeV and mean energy densities from 0.8 to 2.1 MeV/mum, respectively). The sample responses are studied as a function of the ~(12)C energy and penetration depth, both in the positive and negative bias polarization. The experimental results clearly show that, when the detector is previously driven in the so-called pumped state by ~(90)Sr beta-particle irradiation, a different behavior of signals is observed in the positive and negative polarization states. The data are analysed in the framework of a properly modified Hecht model were the different behavior of carriers and influence of the variation in the ionization density along the path of the incident particles are considered. As a novelty the inhomogeneous distribution of defects is taken into account. By fitting the experimental curves with the model, a quantitative estimate of the defects distribution and of the correlated man drift distance for electron and holes can be obtained. A good agreement is observed, thus allowing a better undestanding of the diamond growth.