Correlation of 2D-interface defect density and electrical parameters of a GZO/p-Si heterojunctions: application to three surface morphologies

This study emphasizes the effect of silicon (Si) surface morphology on the optoelectronic and electrical properties of gallium doped ZnO (GZO)/p-Si heterojunctions. Thus, the 2D mapping of the interface defect density (N-ss) is carried out by combining micro-wave photo-conductance decay (mu W-PCD) and surface photovoltage (SPV) measurements. The Nss is found to vary between 6.24 x 10(13) cm(-2) and 5.20 x 10(14) cm(-2) depending on the surface morphology. Besides, the electrical parameters (ideality factor n, barrier height Phi(B) and series resistance R-s) of the obtained structures are determined from dV/d(ln(I)) vs. I plot and Cheung's function. The estimated values lie between 1.2 and 2.8 for the ideality factor and between 12 Omega and 132 Omega for R-s. These parameters are used to extract the N-ss values which are found to be in good agreement with those obtained from the 2D mapping. The variation of the interface defect density reveals that the defect energy level is located in the lower part of the band gap, suggesting a heavy pinning of the Fermi level. The current-voltage characteristics reveal that the charge carrier transport is governed by three conduction mechanisms which are the tunneling assisted recombination, the space-charge-limited current (SCLC) and the tunneling current. The variation of the electrical parameters (n and R-s) along with the barrier height, was found to be related to the variation of the interface defect density.