STUDY ON THE CURRENT TRANSPORT CHARACTERISTICS OF SI NANODOTS IN A LUMINESCENT SILICON RICH SILICON NITRIDE THIN FILM

• Main Authors: Zingway Pei, 裴靜偉
• Other Authors: Huey-Liang Hwang
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/75872484988207504061

博士 === 國立清華大學 === 電機工程學系 === 92 === In this thesis, we produced Si-rich silicon nitride thin film by plasma enhanced chemical vapor deposition. The flow rate of N2 gas precursor was used as the varying parameter from 2 to 160 sccm while keep the flow rate of SiH4 at 40 sccm. The silicon based EL device was made by employing PECVD deposited a-SiNx: H thin films as the active layer in the ITO glass / a-SiNx: H (80nm) / Al structure. The EL spectrum was to have a wide distribution from 400 to 750nm and was extensively blue-shifted as compared to the PL spectrum. The electro-luminescence was suggested as being due to gap states’ impact ionized as a result of high electric field and recombination in the luminescent centers in a-SiNx: H thin films. The existence of the Si-Si4 phase in the annealed silicon nitride was confirmed by the appearance multi-peaks in the Si 2p binding from the XPS spectra. Silicon nanodots were also observed in the α-SiN0.56: H by cross section TEM image. The size of the Si nanodots after the rapid thermal annealing was between 2 and 4nm has a mean diameter of 3 nm with density of 7X1011/cm2. Current-voltage characteristics were applied to investigate the electrical transport properties. The structure for measurement studies consist an Au/Al metal as the top gate, a layer of silicon nitride films with different compositions on n or p type Si substrate. The structure ensures either electrons or holes as dominated carriers for investigations. NDR effects were observed at low field in the form of a current jump (electron tunneling) or current peak (hole transport). A double barrier band diagram is suggested to explain this current transport. The NDR is attributed to the Si nanodots related transport. With the sequential stress experiment, the traps assist tunneling might incorporated in the Si nanodots related transport. Current-voltage measurement on the diodes with different Si contents was also performed. The peaks shift with the Si contents at low bias was attributed as the transport through the energy level of Si nanodots. The disappearance of NDR effects at samples contain less Si contents points out a boundary between the resonant tunneling and F-N tunneling. The frequency-dependent capacitance-voltage (C-V) spectroscopy was applied to investigate on the carrier dynamics in Si nanodots embedded structure. The negative differential resistance (NDR) region in current-voltage (I-V) characteristics was found consistent to the dot related capacitance in multi-frequency capacitance voltage characteristics further implies the Si dot related transport mechanism. An equivalent circuit model was suggested to explain the frequency dependence. The transport time were estimated based on this model. The energy levels in the Si-rich silicon nitride films using the parameter direct or indirect form the measurement results. The boundary of NDR effect between N30 and N70 conditions can be explained by the band diagrams. The transport characteristics for thin silicon nitride film contain Si nanodots were investigated. This NDR effect due to the Si nanodots related transport was found in highly Si content sample. Charging carriers in the silicon nitride film was found at less Si contents sample. The results of this work suggest the Si rich silicon nitride is potentially for non-volatile memory and NDR device applications.