SiOx films deposited by HFCVD: Their conduction response to light and intrinsic photovoltaic effect

Abstract

In this work, the presence of photoconduction and photovoltaic effects in MOS-type structures manufactured using off-stoichiometric silicon oxide (SiOx) deposited by HFCVD technique is reported. Current-voltage measurements under dark and illumination conditions were carried out. A photoconductive response of 1µA was found under illumination conditions, such current is about 4 orders of magnitude greater than its value in dark condition which was about 100pA. The reported MOS-type structures with SiOx as dielectric layer undergo a change in the charge conduction mechanisms of the injection current, exhibiting a transition from the Hopping to Schottky mechanism, which is dependent on the hydrogen amount and the deposition parameters of SiOx films. A starting charge conduction state identified as the Space Charge Limited Conduction mechanism (SCLC) is found when applying low voltages. Additionally, the photovoltaic effect was obtained and studied for these types of structures, being corroborated by current-time and voltage-time measurements in dark and illuminations conditions without applied bias. The spectral response and quantum efficiencies were also obtained, where the best internal quantum efficiency was 25.59%. The photoconductive effect is present for structures with SiOx films without annealing, while the ones with SiOx films that have thermal annealing exhibit the photovoltaic effect. The studied structures are suitable for photovoltaic applications and they have additional advantages namely: a short time of deposit (3 min) by using the HFCVD technique, and a single MOS-type structure.