In this paper, a series of boron doped microcrystalline hydrogenated silicon-germanium (p-μc-Si1-xGex:H) was deposited by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) from SiH4 and GeF4 mixtures. The effect of GeF4 concentration on films' composition, structure and electrical properties was studied. The results show that with the increase of GeF4 concentration, the Ge fraction x increases. The dark conductivity and crystalline volume fraction increase first, and then decrease. When the GC is 4%, p-μc-Si1-xGex:H material with high conductivity, low activation energy (σ = 1.68 S/cm, Eg = 0.047 eV), high crystalline volume fraction (60%) and with an average transmission coefficient over the long wave region reaching 0.9 at the thickness of 72 nm was achieved. The experimental results were discussed in detail.
This letter introduces a 4th order active RC complex filter with 1.5MHz center frequency and 1MHz bandwidth. The total harmonic distortion of the filter is less than –60dB and the image rejection ratio is greater than 60dB. A novel technique is also proposed in this letter to automatically adjust the variation of the time constant. The advantages of the proposed method are its high precision and simplicity. Using 5bits control words, the tuning error is less than ±1.6%.
Chen Dianyu Qi Feitao Sun Weiming Qin Shicai Xiong Shaozhen
A dynamic phosphor-silicate glass (PSG) gettering method is proposed in which the processes of the gettering of Ni by PSG and the crystallizing of α-Si into poly-Si by Ni take place simultaneously.The effects of PSG gettering process on the performances of solution-based metal induced crystallized (S-MIC) poly-Si materials and their thin film transistors (TFTs) are discussed.The crystallization rate is much reduced due to the fact that the Ni as a medium source of crystallization is extracted by the PSG during crystallization at the same time.The boundary between two neighbouring grains in S-MIC poly-Si with PSG looks blurrier than without PSG.Compared with the TFTs made from S-MIC poly-Si without PSG gettering,the TFTs made with PSG gettering has a reduced gate induced leakage current.
This paper investigates a simplified metal induced crystallization(MIC) of a-Si,named solution-based MIC(S-MIC).The nickel inducing source was formed on a-Si from salt solution dissolved in de-ionized water or ethanol.a-Si thin film was deposited with low pressure chemical vapour deposition or plasma enhanced chemical vapour deposition as precursor material for MIC.It finds that the content of nickel source formed on a-Si can be controlled by solution concentration and dipping time.The dependence of crystallization rate of a-Si on annealing time illustrated that the linear density of nickel source was another critical factor that affects the crystallization of a-Si,besides the diffusion of nickel disilicide.The highest electron Hall mobility of thus prepared S-MIC poly-Si is 45.6 cm2/(V · s).By using this S-MIC poly-Si,thin film transistors and display scan drivers were made,and their characteristics are presented.
The hydrogen passivation is adopted to enhance the performance of poly-Si crystallized by YAG laser annealing(LA polySi).The effects of passivation time,passivation power and passivation temperature on the hall mobility of the LA poly-Si are investigated and the mechanism of the hydrogen passivation is preliminarily analyzed.It is found that the effect of the hydrogen passivation on the qulity of YAG laser annealed poly-Si is also correlated with the deposition method and the defect type in it.
