Electronic transitions of electrons bound to phosphorus donors in diamond

A set of phosphorus doped CVD diamond films was investigated by infrared absorption spectroscopy. The photo-ionisation continuum intensity increases consistently with the phosphorus concentration. Two peaks, at 523 and 562 meV, were observed for the first time, and are attributed to electronic transitions from the phosphorus ground level to the 2P0 and 2P+/− excited states, in good agreement with the effective mass approximation. The optical ionisation energy deduced is 600 meV (±20 meV), consistent with Hall effect measurements.