10⁶ cm^2/(V.s) Carrier Mobility Measured in Ultra Pure Diamond by Time of Flight Electron Beam Induced Current

Diamond is a very promising material for various applications, and understanding its basic properties is key for the development of future devices. In particular, the low-field mobility of holes has never been measured below ∼80 K in ultra-pure diamond. In order to measure this mobility, we developed an innovative Time of Flight electron Beam Induced Current (ToF-eBIC) technique. A 1 ns pulsed electron beam was made to impact the diamond semiconductor, inducing charge carrier creation and motion through the 546 μm thick bulk diamond, under the influence of an applied electric field. The resulting signal was analysed using the transient time technique. Thus, the velocity of electrons and holes was assessed as a function of the temperature from 13 to 300 K and as a function of the electric field with values ranging from 1.5 to 9200 V/cm. A low-field mobility value of 1.03 x 10⁶ cm² /(V.s) was measured for holes at 13 K, demonstrating that diamond is a suitable material to transport charge carriers in a ballistic regime at a scale of ten micrometers.