RITE-ITAMI LABORATORY in Sumitomo Electric Industries Ltd. 

For the preservation of earth environment, it is enevitable to minimize imperfect combustibles of hydro-carbons and NOx which are exhausted from automotives. For that purpose, it is neccessary to develop sophisticated engine combustion system associated with the electrical control system, which will be realized by refractory semiconductor devices.

In this research, the refractory semiconductor device using diamond/cubic boron nitride (cBN) heterojunction material system is employed, and research activities on hetero-epitaxial growth of diamond on cBN, doping technologies, refractory ohmic contact and overall device technologies were carried out.

Utilizing microwave plasma deposition technology, diamond is epitaxially grown on almost lattice matched crystal of cBN without inter-diffusion of consituents. Successful growth were also obtained for the high concentration doping of Si into cBN to form n-type channel and B into diamond to form p-type channel. In general, the ohmic contact plays important roll in refractory semiconductor devices, because of its deterioration for high temperature circumstances. In this research, the multi-layered metal structure of Ti/Mo/Au is developed and confirmed to have super characteristics of refractory ohmic, such as 400hr at 800C storage, which is the world record at this moment. Combining these technologies, diamond/cBN heterojunction diode is developed for the first time in the world to be operated at 500C. A numbers of circuits will be developed using this device to realize the refractory electrical controll system for the sophisticated engine combustion system.