Optical characterization of CVD-diamond films

The fundamental band edge of synthetic diamonds has been characterized by d ifferential reflectance (DR) and cathodoluminescence (CL) spectroscopies. W e compared DR and CL spectra of a high-pressure-high-temperature (HPHT) syn thetic diamond, a boron-doped homoepitaxial single-crystal film, and a boro n-doped polycrystalline film on Si(OO I). The CL spectrum of the HPHT diamo nd shows strong free exciton luminescence, while that of the boron-doped di amond film shows impurity bound exciton luminescence. The DR spectrum obtai ned from the HPHT synthetic diamond shows interband transitions assisted by phonon emission. On the other hand, it was found that the zero-phonon tran sition becomes dominant in the polycrystalline film. Furthermore, we invest igated higher interband transitions localized in the Brillouin zone by mean s of a newly developed technique called electron-beam electroreflectance sp ectroscopy.