The Electronic Structure of Phosphorus in n-Type CVD Diamond Films: Revised

In this paper we apply the quasi-steady-state photocurrent (PC) technique and photothermal ionisation spectroscopy (PTIS) at various low temperatures to study n-type P-doped CVD diamond samples, prepared under different doping conditions. The low temperature photocurrent spectra for 500 ppm P-doped films show phonon-assisted oscillatory photoconductivity with more and sharper minima than for the 1000 ppm sample. The 500 ppm PH3/CH4 doped samples exhibit at this moment also the highest reported Hall mobility at RT of 240 cm2 V–1 s–1, pointing to a better film quality with less stress, resulting in less broadening of the defect levels in the band gap. Minima in the photocurrent signal that are separated by 155 meV can be grouped. This energy corresponds to the LO phonon at the conduction band minimum, located along the Δ-axes of the diamond band structure in the [100] direction. It is created when an electron thermalises out of the conduction band into an excited level.