High Temperature Rectifying Contacts on Semiconducting Diamond Using Doped Silicon
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HIGH TEMPERATURE RECTIFYING CONTACTS ON SEMICONDUCTING DIAMOND USING DOPED SILICON V.VENKATESAN, D.G.THOMPSON AND K.DAS Kobe Steel USA Inc., Electronic Materials Research Triangle Park, N. C. 27709.
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ABSTRACT High temperature rectifying contacts have been fabricated on naturally occurring lib semiconducting diamond crystals using highly doped Si. Polycrystalline Si deposited by low pressure chemical vapor deposition (LPCVD) and amorphous Si deposited by sputtering were investigated. Following LPCVD deposition, the polycrystalline Si filn was doped with P by solid state diffusion at a temperature of 900 0 C using a POCI3 source. Boron doped and As doped Si films were deposited by sputtering from highly doped Si targets. Current-voltage measurements were performed on the fabricated P doped, B doped and As doped Si contacts from room temperature up to -400'C. In all cases, the contacts yielded excellent rectification in the temperature range investigated. Current conduction in doped Si/diamond systems appears to be space charge limited. The position and concentration of deep levels in a natural lib diamond crystal have been determined from an analysis of space charge limited current-voltage (I-V) characteristics. INTRODUCTION There is at present a tremendous interest in the growth and use of diamond for high temperature, high speed and high power device applications [1-3]. A number of these devices rely on a rectifying metal/semiconductor contact for their operation. Rectifying contacts have been reported for naturally occurring semiconducting diamond single crystals [4], synthetic B doped diamond crystals [5] and CVD grown homoepitaxial [6,7] and polycrystalline diamond films [8,9]. Polycrystalline Si has been suggested as a suitable material for the formation of Schottky contacts on diamond [10]. Ishii et al. [11] have disclosed the formation of an ohmic contacts using n-silicon on ndiamond and p-silicon on p-diamond. In this paper we report the fabrication and electrical characteristics of rectifying contacts on semiconducting diamond using doped Si contacts. All the three types of contacts, P doped polycrystalline Si, B doped Si and As doped Si, show stable rectification up to a measurement temperature of -400'C. Moreover, the I-V characteristics of these contacts on diamond indicate that the dominant transport mechanism is Mat. Res. Soc. Symp. Proc. Vol. 270. D1992 Materials Research Society
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space charge limited current (SCLC) conduction in the presence of deeplevel states. A simple analysis of the forward characteristics has been employed to determine deep-level parameters in the natural diamond crystals. EXPERIMENTAL DETAILS All the naturally occurring lib semiconducting diamond crystals (100) used in this study were polished and thoroughly cleaned to remove any graphitized layer left on the surface due to polishing. A solution of CrO3+H 2 SO4 heated to -200'C was used to remove any graphite on the surfaces of the diamond single crystals. These samples were subsequently, clea
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