Valley-Polarized Charge Transport in Diamond

Abstract: Diamond is a wide bandgap semiconductor with extreme properties such as high thermal conductivity, high breakdown field and high carrier mobilities. These properties together with the possibility to synthesize high purity Single-Crystalline (SC) diamond by Chemical Vapor Deposition (CVD), makes it a really interesting material for electronic devices. The low impurity concentration achieved when fabricating diamonds by CVD allows for a detailed study of the intrinsic electronic properties of diamond, especially at low temperatures when the carrier scattering rate is low.During the last few years, our group has presented two new phenomena discovered in SC-CVD diamond at temperatures below 150 K. For the very first time, Negative Differential Mobility (NDM) and valley polarization have been observed in diamond. NDM occurs at a temperature range of 110 to 140 K and at an electric field range of 300 to 600 V/cm and has been explained by electron repopulation between different valleys. At temperatures below 100 K, stable valley polarization has been observed due to the low phonon scattering rate in diamond that enable electrons to reside in one valley.This licentiate thesis will give a short review on electronic properties and charge transport in diamond. It will also present the two discovered phenomena and the methods used to observe them. There will be further discussions of how these discoveries can be used for making future devices, such as the Transferred-Electron Oscillator (TEO) and valleytronic devices.