Study of Metal/Semiconductor Interfaces

点击翻译按钮获取中文摘要

We have studied the interface structure and its electronic characteristics between various metals and wide-gap semiconductors, paricularly GaN and tetrahedral amorphous carbon films. Both of these films recently attract considerable interests as useful materials for new functional electronic and photonic devices. However, the metal contacts to these new materials usually show poor characteristics such as a very high contact resistivity, and the problem remains yet to be solved.Our conclusions and proposals in the present research project include ;1.We have presented a new type of wavelength dispersive x-ray spectrometer with a multi-capillary x-ray lens. A multi-capillary x-ray lens, a device that collects fluorescent x-rays from a selected sample area of 0.1 mm dia. or less and collimates them into a nearly parallel beam form, is combined with conventional flat crystals. Since we can focus the excitation x-ray beam down to about 10 micron meters using a focussing lens, the present spe … More ctrometer enables us to examine quite a narrow and local area such as the metal/semiconductor interfaces with the convenient XRF in air.2. Several metals have been tested as candidate materials for ohmic contacts top-GaN.At the present stage the best metal that we propose is the Pd/Nb/Au layered structure. The impurity H in p-GaN, which sticks the dopant Mg and consequently decreases the activation coefficient down to only 1 % or even less, is effectively deprived and trapped by the electrode metals resulting in a stable and relatively low-resistivity contact. However, the resistivity is in the order of〜mΩ・cm2, not low enough for practical applications. In addition to the proper choice of electrode metals, co-doping ofimpurity oxygen or silicon together with Mg seems to be necessary to make the acceptor levels sufficiently shallower for eventualy practical low-resistivity contacts.3. The effect of different metal back contacts on the electrical and structural properties of the tetrahedral amorphous carbon (ta-C) has been studied using I-V measurements, Raman and MeV ion scattering spectrometries. Various metal such as Al, Au, Cr, Mo, Cu, W, and Ti have been used as back contacts of ta-C grown by a pulsed cathodic arc system, The electrical measurements and Raman response showed that the back contact does influence the emission properties of ta-C, in a good agreement with the metal/ta-C interface morphologies and/or inter diffusions detected by MeV ion scattering.Also clearly shown is that the deposition condition of ta-C films affects the interface properties. Less