Time-of-Flight Characterization of Single-crystalline CVD Diamond with Different Surface Passivation Layers
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Time-of-Flight Characterization of Single-crystalline CVD Diamond with Different Surface Passivation Layers. Kiran Kumar Kovi1, Saman Majdi1, Markus Gabrysch1,Ian Friel2, Richard Balmer2 and Jan Isberg1. 1. Division of Electricity, Department of Engineering Sciences, Uppsala University, Box 531, Uppsala, Sweden. 2 Element Six Ltd., Kings Ride Park, Ascot, Berkshire SL5 8BP, United Kingdom ABSTRACT The electronic properties of diamond, e.g. a high band-gap and high carrier mobilities, together with material properties such as a very high thermal conductivity, chemical inertness and a high radiation resistance makes diamond a unique material for many extreme electronic applications out of reach for silicon devices. This includes, e.g. microwave power devices, power devices and high temperature electronics. It is important to have an effective passivation of the surface of such devices since the passivation determines the ability of the device to withstand high surface electric fields. In addition, the passivation is used to control the surface charge which can strongly influence the electric field in the bulk of the device. It is possible to measure sample parameters such as electron and hole drift mobilities, charge carrier lifetimes or saturation velocities using Time-of-flight (ToF) method. The ToF technique has also been adapted for probing the electric field distribution and the distribution of trapped charge. In this paper we present new data from lateral ToF studies of high-purity single crystalline diamond with different surface passivations. Silicon oxide and silicon nitride are used as passivation layers in the current study. The effect of the passivation on charge transport is studied, and the results of different passivation materials are compared experimentally. INTRODUCTION Diamond with its attractive material properties like high band gap (5.47 eV), high thermal conductivity, high breakdown voltage, high break down field strength, high mobilities, radiation hardness, chemically inert etc are interesting to be used in electrical applications for high power, high frequency devices. To realize electronic devices based on thin film SC-CVD diamond, certain designs and fabrication techniques different from silicon technology are needed as silicon has shallow dopants. High electron and hole mobilities were reported in diamond in [1]. Delta doping in SC-CVD diamond is reported [18] for realizing high mobility devices. In delta doping, a very thin layer (few nm) of highly boron doped (> 1021 /Cm3) is incorporated between intrinsic diamond layers during growth. But, for efficient functionality, reproducibility, to reduce the surface leakage and to improve surface properties, effective surface passivation is required. In the current work, Silicon oxide (SiO2) and Silicon nitride (Si3N4) which are often used as passivation materials for electrical passivation of devices were used as passivation layers. Certain methods to characterize these layers are needed to know the devices properties and hence Time-of-flight te
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