Device Grade B-Doped Homoepitaxial Diamond Thin Films

We review our recent results on properties of high quality B-doped homoepitaxial diamond thin films grown by chemical vapor deposition (CVD) by using trimethylboron (TMB) as a B source gas. The conventional (one-step) and the two-step growth methods were used for film preparation. The latter realized smooth surface without any non-epitaxial crystallites (UCs). The films showed a sharp Raman shift peak at 1332 cm—1, a strong free-excitonic emission at room temperature, and high Hall mobility as high as 1000 cm2/Vs or more, indicating high-quality diamond. We also successfully realized resistivity control of the films in a wide range from 100 to 105 Ω cm due to low compensation ratio. Using the two-step growth method, Schottky junctions with the ideality factor n of 1.1 or less and undetectable leakage current could be prepared between various metals such as Al, Zn, Cr, Ni, Au or Pt and oxidized B-doped CVD diamond films. In particular, we successfully made nearly ideal Schottky junctions using highly B-doped films in the order of 1017 cm—3, indicating that the quality of the present B-doped films is comparable with or higher than those of conventional semiconductors such as Si and GaAs.