Effect of Boron Incorporation on Slow Interface Traps in SiO2/4H-SiC Structures

The reason for the effective removal of interface traps in SiO2/4H-SiC (0001) structures by boron (B) incorporation was investigated by employing low-temperature electrical measurements. Low-temperature capacitance–voltage and thermal dielectric relaxation current measurements revealed that the density of electrons captured in slow interface traps in B-incorporated oxide is lower than that in dry and NO-annealed oxides. These results suggest that near-interface traps can be removed by B incorporation, which is considered to be an important reason for the increase in the field-effect mobility of 4H-SiC metal–oxide–semiconductor devices. A model for the passivation mechanism is proposed that takes account of stress relaxation during thermal oxidation

Methane flux of leaves in a tropical rainforest and a temperate conifer forest

We measured methane (CH[4]) fluxes of leaves growing in a tropical rainforest and a temperate conifer forest using the closed static chamber method. Leaf samples were chosen from the canopy and forest floor of a tropical rainforest at Pasoh Forest Reserve, Peninsular Malaysia and a temperate forest at Kiryu Experimental Watershed (KEW), central Japan. At Pasoh, we sampled four species from the canopy (Xanthophyllum stipitatum, Dipterocarpus sublamellatus, Ptychopyxis caput-medusae, Neobalanocarpus heimii) and four species from the forest floor (Alphonsea maingayi, Rinorea anguifera, Macaranga lowii, Neobalanocarpus heimii). The leaves of Elaeis guineensis were also sampled at an oil palm plantation near the forest reserve area. At KEW, we sampled the leaves of Chamaecyparis obtusa, from both the top (18 m) and middle (16 m) of the canopy as well as leaves of Eurya japonica at the forest floor. Incubation experiments revealed that CH[4] was emitted from leaves of the tested species sampled at two sites, although CH[4] fluxes showed variations on a daily basis. These results suggest that tree leaves both at Pasoh and KEW might function as a small CH[4]source, but their contribution to the CH[4] exchange of the total forest ecosystem is very small compared to the soil CH[4] flu

Oxidation-Process Dependence of Single Photon Sources Embedded in 4H-SiC MOSFETs

Single photon sources (SPSs) in 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) were investigated using confocal microscope techniques. It was found that SPSs appeared only at 4H-SiC/SiO2 interface regions of wet-oxide C-face MOSFETs. The other regions of MOSFETs such as source, drain and well did not have SPSs. The luminescent intensity of the SPSs at room temperature was at least twice larger than that of nitrogen-vacancy center, in diamond. We examined four types of C-face and Si-face 4H-SiC MOSFETs with different oxidation processes, and as a result, it can be concluded that the formation of the SPSs strongly depended on the preparation conditions of SiC/SiO2 interfaces