Electrical characterization of a-Si:H(n)/c-Si(p) structure

In this study, n-type hydrogenated amorphous silicon (a-Si:H) was fabricated on p-type crystalline silicon (c-Si) substrates to obtain heterojunction diodes. The amorphous films were obtained by the Plasma Enhanced Chemical Vapor Deposition (PECVD) technique. Temperature dependent current-voltage (I-V-T) measurements and investigation of the dc current injection mechanism of a-Si:H(n)/c-Si(p) device structure have been performed. The series resistance (4.6-8.2 Ω) values displayed nearly temperature independent behavior and the ideality factor varied between 2.7 and 1.6 in the temperature range 100-320 K. The forward bias I-V-T characteristics of c-Si/a-Si:H heterojunctions are found to behave like the Schottky junctions where carrier injection is especially influenced by the carrier generation-recombination in the junction interface formed on the amorphous side. The temperature dependent ideality factor behavior shows that tunneling enhanced recombination is valid rather than thermionic emission theory. In the frame of this model, characteristic tunneling energy and characteristic temperature are found to be 9 meV and 1900 K, respectively. It is concluded that fabricate n-type hydrogenated amorphous silicon is a preferable semiconductor material layer with low interface state density because the temperature dependent interface state density calculations give values of the order of 10¹⁴ eV⁻¹ cm⁻².