Electrical and photocurrent analysis of Si-fluorine doped DLC films heterojunctions

摘要

In this work fluorinated DLC films have been deposited in a reactive RF magnetron sputtering system with different concentrations of CF_4 on p-type Si substrates. The effects of fluorine concentration at growth conditions have been studied by electrical DC measurements and photoconductivity. The electrical DC data reveals a Space Charge Limited Current with an activation energy ranging from 50 meV to 140 meV. The photocurrent in the visible region can increase up to two orders of magnitude compared with dark conditions, and dependent on fluorine concentration at growth conditions. The typical photocurrent densities under reverse bias are about 20-40 mA/cm~2. Discreet photoconductivity shows the influence of two contributions, one in the blue-green region (2.4-2.5 eV) and another in the red-near IR region (1.6 eV). Both appear to be dependent on fluorine concentration at DLC growth, especially the last one.