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▲ [15a-4F-8] [Young Scientist Presentation Award Speech] Nano-scale interlayer formation for thermally stable SBD electrical properties
Keywords:diamond,Schottky diode,interface
High temperatures diamond Schottky barrier diodes (SBD) have been developed these last years. In particular, problems of reproducibility and unstable Schottky barrier have been aroused. Zr/diamond SBDs showed rectification gain above 600 K [1]. A native oxide has been found at the Zr/diamond interface by transmission electron microscopy (TEM) [2]. This oxide provided the rectification at elevated temperature, but no ideal Schottky behaviors. In our group, tungsten carbide (WC)/diamond SBDs showed ideal Schottky behavior up to 600 K, after annealing [3]. In addition, stabilization and degradation domains have been identified [4]. Based on TEM, we proposed a model of the WC/diamond interface to explain these thermal modifications. The identification of mechanism undergoing will be helpful to select the ultimate Schottky metal combination.
WC has been deposited by conventional Ar plasma sputtering on lightly boron-doped epilayers whose surfaces were terminated by oxygen. SBDs have been cut in cross section in order to be analysed by TEM. The chemical composition of WC/diamond interface has been obtained by electron energy loss spectrometry (EELS).
The ratio of oxygen peak intensity over carbon pointed out an interfacial oxygen enrichment following the 600 K annealing. At higher temperature, this oxygen signal weakened, indicating an oxygen deficiency. The evolution of oxygen can be interpreted as reactions with tungsten and carbon to form different interlayers. We suggested the WC/diamond interface had a mixed composition over few monolayers before annealing. Oxygen termination might be dissociated by WC bombardment. Then, oxygen could diffuse in the interlayer toward the diamond interface by vacuum annealing at 600 K. The gain in Schottky ideality can be seen as the formation of a homogenous monolayer in contact with diamond. The effect of annealing at 900 K on oxygen is less evident. Catalytic effects of WC are suspected.
References
[1] A. Traore, P. Muret, A. Fiori, et al., Appl. Phys. Lett. 104, 052105 (2014).
[2] J. C. Pinero, D. Araujo, A. Traore, et al., Phys. Status Solidi A 211, 2367 (2014).
[3] A. Fiori, T. Teraji, Y. Koide, Appl. Phys. Lett. 105, 133515 (2014).
[4] A. Fiori, T. Teraji, Y. Koide, Phys. Status Solidi A 211, 2363 (2014).
WC has been deposited by conventional Ar plasma sputtering on lightly boron-doped epilayers whose surfaces were terminated by oxygen. SBDs have been cut in cross section in order to be analysed by TEM. The chemical composition of WC/diamond interface has been obtained by electron energy loss spectrometry (EELS).
The ratio of oxygen peak intensity over carbon pointed out an interfacial oxygen enrichment following the 600 K annealing. At higher temperature, this oxygen signal weakened, indicating an oxygen deficiency. The evolution of oxygen can be interpreted as reactions with tungsten and carbon to form different interlayers. We suggested the WC/diamond interface had a mixed composition over few monolayers before annealing. Oxygen termination might be dissociated by WC bombardment. Then, oxygen could diffuse in the interlayer toward the diamond interface by vacuum annealing at 600 K. The gain in Schottky ideality can be seen as the formation of a homogenous monolayer in contact with diamond. The effect of annealing at 900 K on oxygen is less evident. Catalytic effects of WC are suspected.
References
[1] A. Traore, P. Muret, A. Fiori, et al., Appl. Phys. Lett. 104, 052105 (2014).
[2] J. C. Pinero, D. Araujo, A. Traore, et al., Phys. Status Solidi A 211, 2367 (2014).
[3] A. Fiori, T. Teraji, Y. Koide, Appl. Phys. Lett. 105, 133515 (2014).
[4] A. Fiori, T. Teraji, Y. Koide, Phys. Status Solidi A 211, 2363 (2014).