A lateral time-of-flight system for charge transport studies

A measurement system for lateral ToF charge carrier transport studies in intrinsic diamond is described. In the lateral ToF geometry, carriers travel close to the sample surface and the system is therefore particularly suited for studies of thin layers as well as the influence of different surface conditions on transport dynamics. A 213 nm pulsed UV laser is used to create electron–hole pairs along a line focus between two parallel metal electrodes on one surface. The use of reflective UV-optics with short focal length allows for a narrow focal line and also for imaging the sample in UV or visible light without any dispersion. A clear hole transit was observed in one homoepitaxial single crystalline diamond film for which the substrate was treated by a Ar/Cl plasma etch prior to deposition. The hole transit signal was sufficiently clear to measure the near-surface hole drift mobility of about 860 cm2/Vs across a contact spacing of 0.3 mm.