The current–voltage and capacitance–voltage characterization of the Au/Methylene Blue/n-GaAs organic-modified Schottky diodes

We report the electrical properties of the Au/n–GaAs devices with and without thin organic interface layer. Methylene blue (MB) is a heterocyclic aromatic chemical compound with the molecular formula C16H18N3SCl. The MB layer was formed by spin coating technique on chemically cleaned gallium arsenide (GaAs) substrate. The current–voltage (I–V) and the frequency dependent capacitance–voltage (C–V) characteristics of the Au/MB/n–GaAs metal-insulator-semiconductor (MIS) and Au/n–GaAs metal-semiconductor (MS) devices have been investigated at room temperature. The MS and MIS devices I–V characteristics the showed a good rectification, and they were analyzed based on the thermionic emission (TE) theory. The ideality factor (n) and the barrier height (Φb(IV)) from the I–V characteristics was determined as 1.131±0.006 and 0.782±0.005 eV for MS device and 1.336±0.057 and 0.950±0.008 eV for MIS device, respectively. A Cheung’s method and modified Norde's function has been used to extract the parameters including the (Φb) and the series resistance (RS). Also the values of the barrier height obtained from the C–V measurements (Φb(CV)) of the MS and MIS was 0.863±0.034 eV and 1.187±0.093 eV, at 1 MHz, respectively.Distributions of the interface state density (Dit) of the MS and MIS devices were derivate from I–V and C–V measurements. Our results indicates that the Au/MB/n–GaAs device had lower interface state density values than the Au/GaAs device. Also non-saturated reverse bias current investigated by the using a Pole-Frenkel emission model. Furthermore, the optical and morphological properties of MB layer were investigated by the Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and UV-vis Spectrophotometer (UV-vis).Finally, we showed that, increasing Φb and decreasing Dit and improving electrical parameters of MIS devices indicates that, thin MB interface layer could prefer for modification of Au/n–GaAs devices.