English abstract
Metal-gallium nitride (GaN) interfaces play very important roles in many high-performance optoelectronic and power devices. Accurate preparation of the GaN surface and a precise control of the conditions of the formation of both ohmic and Schottky contacts are essential for developing GaN-based optoelectronic and electronic devices. Since the electrical characteristics of the Schottky contact are controlled mainly by its interface properties, thus the study of interface states is essential for the understanding of the electrical properties of GaN based Schottky contacts. The structural properties of the as-grown GaN have been characterized
using RBS/C and HRXRD techniques. Various metals with different work function
on n-type GaN have prepared using e-beam deposition, and their effective Schottky barrier heights (SBHS) and ideality factors (n) have been measured from currentvoltage characteristics over a wide temperature range (80K-400K). A decrease of the thermionic emission mechanism SBHS (POB) and an increase of n with a decrease in the temperature have been explained on the basis of a with the Gaussian distribution of the SBH due to Schottky barrier inhomogeneities at the metal-GaN interface. In addition, from the voltage and temperature dependent of the OB (V,7) and n (1,7) plots; the interface states density (N) and their energy distributions in the Gan band gap were extracted. In parallel, deep level transient spectroscopy (DLTS) analyses were performed to extract quantitative information about the residual defects. From DLTS, two prominent defects D1 and D2 with energy levels below the conduction band, were introduced and assigned to nitrogen-interstitial and nitrogen vacancy, respectively. Finally, our results show that the distribution of interface trap states at metal/GaN is associated with native defects D1 and D2 and is responsible for the lateral inhomogeneities of the Schottky barrier height
