Diode parameters and ultraviolet light detection characteristics of n-type silicon/p-type nanocrystalline diamond heterojunctions at different temperatures

n-Type silicon (Si)/p-type boron (B)-doped ultrananocrystalline diamond (UNCD) heterojunctions were manufactured through coaxial arc plasma deposition, and were examined in terms of the diode parameters and ultraviolet (UV) photodetection at different temperatures. The structure of the deposited films was examined by Raman spectroscopy and a field emission scanning electron microscope. The Raman spectra revealed two wide peaks centered at the positions of 1345 cm⁻¹ and 1585 cm⁻¹ that represented the D and G peaks, respectively. At 300 K, the current density-voltage characteristics showed a considerable high leakage current, which was reduced over two orders of magnitude at 150 K. The ideality factor (n) increased from 2.82 at 300 K to 6.37 at 150 K. In parallel, the barrier height was reduced from 0.75 eV at 300 K to 0.43 eV at 150 K. Through Norde's approach, the series resistance values were found to be 4.33 kΩ at 300 K and 277.52 kΩ at 150 K, which increased by decreasing the temperature because of the increased n and the lack of carrier mobility in the B-doped UNCD/a-C:H films. Although a small UV response was observed at 300 K, the photocurrent at 150 K was over two orders of magnitude above the dark current at zero voltage. The detectivity values at 0 V were 2.37 × 10⁹ Hz^1/2 cm/W and 1.34 × 10¹⁰ Hz^1/2 cm/W at 300 K and 150 K, respectively. This research proposed a comprehensive study on the n-type Si/p-type UNCD heterojunctions as candidate photodiodes for UV photodetection applications.