Investigation Of Electronic Transport Properties In Nano Schottky Diodes

The demand for electronic and optoelectronic devices that have higher function and precision is growing,and significant efforts have been directed toward investigating nano-interfaces and nanostructures.Nanoparticles?NPs?,nanowires,and nanorods have exhibited excellent electrical,optical,and thermal properties and can be the cornerstone for future optoelectronic nanodevices and electronic devices.It is necessary for us to investigate those electrical properties of such nanostructures that can be applied to various metal-semiconductor?MS?junction-based optoelectronic devices,especially the relationship between transport properties and the device size.This paper summarizes the development of low-dimensional nanomaterials and the phenomenon of thermionic emission at nanometer size.The electrical transport properties of metal-semiconductor contacts and the basic theory of Schottky barrier are discussed.The main methods of extracting Schottky parameters and the main transmission mechanism of Schottky parameters are given.First,the Pt nano-film Schottky diodes on Ge substrate have been fabricated to investigate the effect of annealing temperature on the characteristics of the device.The germanide phase between Pt nano-films and Ge substrate changed and generated interface layer PtGe at 573 K and 673 K,Pt₂Ge₃ at 773 K.The current-voltage?I-V?characteristics of Pt/n-Ge Schottky diodes were measured in the temperature range of183-303 K.Evaluation of the I-V data has revealed an increase of zero-bias barrier height?_B0 but the decrease of ideality factor n with the increase in temperature.Such behaviors have been successfully modeled on the basis of the thermionic emission mechanism by assuming the presence of Gaussian distributions.The variation of electronic transport properties of these Schottky diodes has been inferred to be attributed to combined effects of interfacial reaction and phase transformation during the annealing process.Therefore,the control of Schottky barrier height at metal/Ge interface is important to realize high performance Ge-based CMOS devicesWhat is more,gold nanoparticles?Au NPs?were distributed on an n-Ge substrate using the colloidal NP deposition method to form Au NP/Ge Schottky diodes?SDs?,and the current transport properties of these nano-SDs were studied.The current density-voltage?J-V?characteristics were measured on each nanometer-sized Au particle using a conducting atomic force microscope?C-AFM?.These Au NP/Ge diodes showed a rectifying behavior.According to the thermionic emission?TE?model,the effective Schottky barrier height?SBH?and ideality factors n were obtained.The SBH for the Au NP/Ge diodes ranges from 0.22 to 0.30 eV and the ideality factor ranges from3.8 to 8.6.The current density and the barrier height increase while the ideality factor decreases with increasing Au NP diameters.This indicates that the tunneling effect is enhanced because of the narrowed depletion width and decreased size of the Au NP/Ge SDs.To compare the electrical behavior with Au NP/Ge diodes,the Au thin film/Ge diodes were also prepared and their SBHs were much larger because of the image-charge lowering effect and the tunneling effect in Au NP/Ge diodes.At last,the research results of the dissertation were summarized and the existing shortcomings were admitted.Besides,the points worthy of further research were recommended.