Characterization of the MoO3 films grown by molecular beam epitaxy on c-plane sapphire substrates was conducted. X-ray diffraction and Raman scattering measurements revealed that amorphous, (100) β-phase, and (010) α-phase MoO3 films were preferentially grown at 150, 200, and 350 °C, respectively. Their optical bandgap energies were estimated to be ∼3.5 eV for the amorphous, ∼3.7 eV for the β-phase, and ∼4.1 eV for the α-phase films. Intense near-band-edge emission was observed from the α-phase films even at room temperature. Postgrowth annealing effect on the β- and the α-phase MoO3 films was also studied, and it was found that the β-phase films were completely transformed into stable α-phase films at 600 °C, accompanied by a bandgap increase to ∼4.1 eV.

We investigated the channeling implantation of dopant ions into 4H-SiC in detail. The advantages of channeling implantation were clarified by both experimental and Monte Carlo simulation. Extremely abrupt deep profile with box-like can be formed by channeling implantation of Al and P ions. In the case of B and N ions, retrograde-like profile can be obtained by channeling implantation. The unique dopant profile can be realized by channeling implantation. Both vertical and lateral straggling becomes small by using channeling implantation for Al ions. This technique should contribute to improve the device performance such as gate pitch scaling and low specific on-resistance.

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