2D-Modelling for the simulation of current-voltage characteristics in polysilicon schottky diode deposited by LPCVD and SAPCVD methods.

The aim of this work is to compare the quality of the Schottky contact obtained between Silver and the un-doped polysilicon layer deposited on glass substrate (Corning 1737 ) by using two techniques: Lower Pressure Chemical Vapor Deposition LPCVD (LPCVD sample) and Sub Atmospheric Pressure Chemical Vapor Deposition SAPCVD (SAPCVD sample). A non ideal measured forward bias I-V characteristic has been observed. The electrical parameters are evaluated such as ideality factor (4.94 and 6.46), barrier height (0.57 eV and 0.60 eV), saturation current (6.74xl0~3 mA and 2.14xl0^2 mA) and series resistance (960Q and 2300Q), respectively on LPCVD and SAPCVD samples. Two-dimensional (2D) model of the I-V characteristics taking into account the localization of traps states in the grain boundaries is developed. We are also considered the U- distribution of traps states in the band gap. A good adjustment is obtained between measurement and simulation of the I-V characteristics and gives the energetic traps states distribution. The comparison of the performance of the two polysilicon layer deposition techniques have been analyzed and discussed. The experimental current curves are well fitted by this model which gives the energetic traps states distribution in the band gap. A good quality polycrystalline can be obtained using LPCVD technique but it is possible to deposit films with SAPCVD technique which it may be interesting candidate for the fabrication of solar cell.