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Abstract: To obtain high current operation of the diamond SBDs, the device should be designed in a vertical type structure in order to minimize the device on-resistance. In this research, we have designed and developed the technology for fabrication of diamond vertical structure Schottky barrier diodes (vSBD) by utilizing Inductively Coupled Plasma etching technique. Free standing CVD grown epilayers (p+/p− =100μm/5μm) were obtained by removing the base Ib substrate on which the epi-layers were grown, using ICP etching process. After ICP etching, ohmic contact (Ti/Pt/Au) was made at the bottom of p+ layer, and Schottky contact (Mo) was made at top side on oxidized surface of p− layer, to realize Diamond/Mo vSBDs and were analyzed for their electrical characteristics. The SBDs showed a reproducible ideality factor close to 1.0, and a barrier height of 1.4eV, with a small standard deviation of 0.06 and 0.12eV respectively. Diodes in the vertical structure exhibited R on with a battery uniformity irrespective of their location on the wafer, compared the diodes in a pseudo-vertical structure. Room temperature I–V analysis of the fabricated vSBDs (70μm size) exhibited a high forward current density of 2980A/cm2 (=0.115A) with a low R onS of 8mΩcm2, which could be attained due to the vertical geometry of the diodes. At the high temperature operation, still higher current density could be obtained. Satisfactory reverse blocking characteristics also could be achieved with a breakdown field of 2.7MV/cm for small size diodes. [ABSTRACT FROM AUTHOR]

Abstract: The superior material properties of diamond power semiconductor devices make them a crucial technology. For high-voltage applications, optimized structures such as electric field edge termination are required for devices. In this paper, we have investigated the optimization of electric field relaxation techniques in oxygen-terminated p-type diamond Schottky barrier diodes and made comparisons with regard to electric field crowding and breakdown in oxides. Due to the low dielectric constant of diamond, Al2O3 is appropriate for the fabrication of field plate structures in diamond power devices. [Copyright &y& Elsevier]

Pyramidal and flat-type hillocks, both known for having a threading dislocation in the center, are utilized to examine the effect of surface irregularities on the characteristics of Schottky barrier diodes (SBDs). By performing RAMAN mapping on both hillocks, crystalline imperfections in three dimensions with clear strain are observed. Surface scanning images obtained via atomic force microscopy show an extremely large surface protrusion with a maximum height of approximately 15 nm in the pyramidal hillock. Owing to crystalline imperfections in the threading dislocation region, the SBDs fabricated on the dislocations exhibit inferior forward characteristics. However, high reverse leakage currents are only observed in dislocations on pyramidal hillocks with surface protrusions, whereas low reverse currents are observed in the flat hillock region without surface irregularities. The phenomenon above is consistent with the characteristics of wide bandgap semiconductors such as silicon carbide. [Display omitted] • Effects of surface irregularities on the characteristics of Schottky barrier diodes are studied. • SBDs fabricated on the dislocations exhibit inferior forward characteristics. • High reverse leakage currents are only observed in dislocations on pyramidal hillocks with surface protrusions. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we present planar mesa termination structure with high k dielectric Al2O3 for high-voltage diamond Schottky barrier diode. Analysis, design, and optimization are carried out by simulations using finite element technology computer-aided design (TCAD) Sentaurus Device software. The performances of planar mesa termination structure are compared to those of conventional field plate termination structure. It is found that optimum geometry of planar mesa terminated diode requires shorter metal plate extension (1/3 of the field plate terminated diode). Consequently, planar mesa terminated diode can be designed with bigger Schottky contact to increase its current carrying capability. Breakdown performance of field plate termination structure is limited at 1480V due to peak electric field at the corner of Schottky contact (no oxide breakdown occurs). In contrast, peak electric field in planar mesa termination structure only occurs in the field oxide such that its breakdown performance is highly dependent on the oxide material. Due to Al2O3 breakdown, planar mesa termination structure suffers premature breakdown at 1440V. Considering no oxide breakdown occurs, planar mesa termination structure can realize higher breakdown voltage of 1751V. Therefore, to fully realize the potential of planar mesa terminated diode, it is important to choose suitable high k dielectric material with sufficient breakdown electric field for the field oxide. [Copyright &y& Elsevier]

Abstract: In this study, we investigated non-ideal characteristics of a diamond Schottky barrier diode with Molybdenum (Mo) Schottky metal fabricated by Microwave Plasma Chemical Vapour Deposition (MPCVD) technique. Extraction from forward bias I–V and reverse bias C −2–V measurements yields ideality factor of 1.3, Schottky barrier height of 1.872eV, and on-resistance of 32.63mΩ·cm2. The deviation of extracted Schottky barrier height from an ideal value of 2.24eV (considering Mo workfunction of 4.53eV) indicates Fermi level pinning at the interface. We attributed such non-ideal behavior to the existence of thin interfacial layer and interface states between metal and diamond which forms Metal-Interfacial layer-Semiconductor (MIS) structure. Oxygen surface treatment during fabrication process might have induced them. From forward bias C–V characteristics, the minimum thickness of the interfacial layer is approximately 0.248nm. Energy distribution profile of the interface state density is then evaluated from the forward bias I–V characteristics based on the MIS model. The interface state density is found to be uniformly distributed with values around 1013 eV−1·cm−2. [Copyright &y& Elsevier]

Abstract: Diamond pseudo-vertical structure Schottky barrier diodes (PVSBD) have been fabricated by developing a simple and efficient fabrication technology, in which 14 µm thick p− layer was selectively etched out and ohmic contact was made onto the low resistive p+ layer from topside. The electrical characteristics were evaluated by fabricating Mo/Diamond Schottky barrier diodes in pseudo-vertical structure. With the fabricated structure, a high blocking voltage of 1.6 kV with a low leakage current density in order of 10−7 ~10−6 A/cm2 could be obtained, without any edge termination. The reverse characteristics of the SBDs exhibited a hard breakdown at 1.6 kV, and causing breakdown of the diamond surface itself in a particular case. The later case indicated the presence of sub-surface leak path causing current leakage in one direction in near surface region, and a model has been proposed to explain this. [Copyright &y& Elsevier]