Study of Electrical Properties of Al/Si3N4/n-GaAs MIS capacitors deposited at low and high frequency PECVD

Abstract

This paper presents a study on the fabrication and optimization of GaAs metal-insulator-semiconductor (MIS) structures, comprising Si3N4 as insulator deposited by the PECVD technique. In the RF plasma, the excitation frequencies used, are 380 KHz for the low frequency and 13.56 MHz for the higher frequency. Thanks to the established protocol, it was possible to develop several structures on n-GaAs substrate, to study effect of the surface treatment with sulfur, the deposition of the insulator by PECVD at low and high frequency, as well as the annealing of these structures. Detailed measurements of the capacitance-voltage and conductance-voltage characteristics of the MIS capacity revealed various anomalies. So, the interface properties the structures (MIS) of semiconductor GaAs with insulation metallic have been investigated. The growth of the Si3N4 layer by LF-PECVD on GaAs substrate treated with sulfur has an effect on the electrical properties of the MIS capacitys studied, leading to good capacitance-voltage (C-V) characteristics. The LF-PECVD was also effective in reducing the frequency dispersion, thus suggesting the removal of traps in n-GaAs located near the dielectric/GaAs interface. In contrast, the Si3N4 layer deposited by HF-PECVD method seems to increase the interfacial density of states near the mid-gap leading to a pinning of the Fermi level. At room temperature of measurement, a hysteresis effect was observed showing injection type effect.