Phonon-assisted electronic transitions in phosphorus-doped n-type chemical vapor deposition diamond films

One year ago we published the first results on the electronic structure of the P-level in 1000 ppm PH3/CH4 doped {111}-oriented n-type diamond films, using the quasi-steady-state photocurrent technique (PC) and photothermal ionization spectroscopy (PTIS). In this work we have extended our measurements at various temperatures (4.2-77.4 K) to samples with various doping levels (100, 500 and 1000 ppm PH3/CH4). This allowed us to obtain more precise results for the electronic structure of the phosphorus defect in homoepitaxial n-type CVD diamond films, making use of the 155 meV LO-phonon to explain the oscillatory photoconductivity. These results are confirmed by the PTIS maxima and Fourier transform infra-red (FTIR) data. In addition we present first measurements on a 2000-ppm doped {100}-oriented sample. (C) 2001 Elsevier Science B.V. Ah rights reserved.