Mobility in homoepitaxial doped diamond

Continuous progress in the doping process of diamond has recently resulted in the fabrication of new diamond-based devices for opto- or electronic applications. In the forthcoming years, provided the processing technology can be fully mastered, this will make diamond a key material for manufacturing high-power, high-temperature, and high-speed electronic devices. To optimize the technology, it will be now necessary to have a full picture of transport properties in, both, the p- and n-type materials.

Boron and phosphorus are the most efficient impurities to get p-type and n-type conductivity in diamond with ionisation energies of respectively 0.38 eV and 0.57 eV. The incorporation of B and P atoms is now well mastered during microwave plasma-assisted chemical vapor deposition of (100) and (111) homo-epitaxial diamond layers, making possible the fabrication of elementary electronic devices like Schottky diodes or pn junction.

In this work, the temperature dependence and doping dependence of the carrier mobility in homo-epitaxial B- and P-doped diamond are reviewed. With the help of a theoretical model, the influences of the different scattering mechanisms (phonons and impurities scattering) are described as a function of the temperature for samples in a large doping range. In a first part, a short summary of previously reported results on electron mobility in (111) P-doped diamond will be given [1,2]. In a second part, high hole mobility values (»2000 cm2/Vs) recently reported in the literature in low B-doped (100) diamond are compared with the theoretical model [4] , leading to the determination of the acoustic deformation potential in p-type diamond. Then, the hole mobility doping dependence is established ([B] between 1014 and 1021 cm−3) and the discrepancy observed in Ref. [7] for highly doped samples is explained. Finally, this work clearly shows the advantage to use p-type diamond for d evices working at high temperature due to its very high carriers mobility of 400 cm2/Vs at 500 K, compared to 30 cm2/Vs for holes in 4H-SiC at the same temperature. This confirms the interest to develop new device architectures, like d-doped field effect transistor, based on B-doped diamond able to work at very high frequency and high temperature simultaneously.

References

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2. J. Pernot, C. Tavares, E. Gheeraert, E. Bustarret, M. Katagiri, and S. Koizumi, Appl. Phys. Lett. 89, 122111 (2006).
3. P.N. Volpe, J. Pernot, F. Omnès and P. Muret, Appl. Phys. Lett. 94, 092102 (2009).
4. J. Pernot, P.N. Volpe, F. Omnès, P. Muret, V. Mortet, K. Haenen and T. Teraji, Phys. Rev. B 81, 205203 (2010).
5. K. Tsukioka and H. Okushi, Jpn. J. Appl. Phys., Part 1 45, 8571 (2006).