Effects of series resistance and frequency on the capacitance/conductance –Voltage C/G-V characteristics of Au/GaN/GaAs and Au/GaAs diodes

In order to analyze the effect of the presence of the GaN layer and series resistance, the electrical characteristics of the Au/GaAsand Au/GaN/GaAsdiodes are investigated. The study is realized by a nitridation process of GaAs substrates. The GaN layer is growth in ultrahigh vacuum system with annealing operation realized at 620°C during one hour. (CV) and (G-V) characteristics of Au/GaN/GaAs and Au/GaAs nanostructures at different frequencies have been studied. The estimated values of Rs showed a regular diminution. Since Rs causes errors in the extraction of electrical parameters. Consequently, the measured capacitance (C-V) and conductance (G-V) are corrected to obtain the real “corrected” capacitance (Cc-V) and (Gc-V) of the diodes. Thus, one showed clearly that the values of Cc and Gc increased proportionally with the applied bias voltage. This effect can be observed practically in the accumulation region and for a high frequency (1 MHz). From the C-2-V curves and after correction, the diffusion potential Vd is evaluated to (0.32 V -0.25 V) and the potential barrier φbn is estimated equal to 0.38 eV and 0.31eV for Au/GaN/GaAs and Au/GaAs structures respectively. The states densities Nss for Au /GaN/GaAs and Au/GaAs structures are determined at (Ec-0.2) with and without series resistances and are found equal to (7.3×1012 eV-1 cm-2 and 6.1×1010 eV-1 cm-2) and (9.31×1010 eV-1 cm-2 and 1010 eV-1 cm-2) respectively.