Low Temperature Charge Transport in Diamond

Abstract: Diamond is a wide band semiconductor with fascinating electrical and physical properties. It has high thermal and electrical conductivity, high electrical breakdown field, high radiation hardness and is chemically inert. These properties make diamond an excellent material for high power electronics, high frequency electronics, particle detectors and for electronics in hazardous environments. Moreover, diamond has been suggested for applications in valleytronics.Valleytronics is a term for semiconductor technology that exploits minima in an energy band, so called valleys. In diamond there are six of these valleys in the conduction band and the conduction electrons resides in one of these six valleys at low temperatures. The valley an electron is in, its valley polarization, affects how it behaves in an electric field. The valley polarization along with an understanding of the electron-phonon scattering processes makes a good framework for understanding of electron transport in diamond. In this thesis, both of these topics have been explored, with the purpose of understanding low temperature electron transport in diamond. A detailed description of low temperature charge transport is relevant for several reasons. Firstly, it can help with understanding the charge transport in e.g. detectors. Secondly, it gives more degrees of freedom when designing new electronics.   In this thesis, both experiments and simulations has been used investigate low temperature transport in diamond. The main experiment method used was time-of-flight were the drift current of valley polarized electrons measured between two contacts. These experiment could then be compared with Monte Carlo simulations. The simulations gave valuable insigne into the dynamics of the electrons. This self-written code for Monte Carlo simulations is described in greater detail in this thesis. Some highlighted results of this thesis are as follows: optical observations of valley polarized diffusion, electrical control of valley polarized currents and the estimations of the acoustic deformation potentials to Du = 18.5 eV and Dd = -5.7 eV. This thesis also includes a more general part about charge transport.