A study of the effect of 1- and 12-MeV electron and Co60 γ irradiation has been made on power p-i- n diodes and Schottky barrier diodes fabricated on the same starting material. A comparison of the results from these two types of structures illustrated the influence of device processing on the type of defects formed by subsequent irradiation. Detailed electrical characterization of the defects demonstrated good consistency between certain elements of the structural nature of the defect, inferred from these measurements, and those already obtained from electron spin resonance (ESR) measurements. Lifetime measurements on the p-i-n diodes indicated that both the A center and the divacancy were active recombination centers. Finally, data are presented on defect and lifetime annealing.

During the past decade there has been a rapid growth of interest in poly-Si for the active device layer in thin film transistors (TFTS) for active matrix flat-panel displays. Whilst the early work, demonstrating the high carrier mobility of these devices, employed processing temperatures of -1000 "C and quartz substrates, this was soon followed by the investigation of lower-temperature processes which were compatible with the use of glass substrates. Some of the key aspects of this work are reviewed in this article: the preparation of the material by direct deposition and by crystallization from a-Si precursors, the characterization of the defect-induced trapping states within the material and their passivation, and the present understanding of the TFT leakage current mechanisms. This work is put into the context of the requirements for active matrix liquid-crystal displays, and, with the understanding and control of poly-Si which has been achieved to date, its application in this area can be expected to increase rapidly in the coming years.

Defect impurity levels have been examined in copper-diffused p-and n-type silicon using deep level transient spectroscopy. Levels at Ev+0.09, Ev+0.23, and Ev+0.42 eV have been observed in both types of material, although the deeper levels were only oberved in n-type material after post-diffusion annealing at 200 °C. Associated with the appearance of these levels in n-type material was another level at Ec−0.16 eV. This may be a further charge state of the center responsible for the Ev+0.23 eV and Ev+0.42 eV levels or the two centers may be decomposition products of a thermally unstable complex. Luminescence measurements have revealed the previously reported Cu-Cu spectrum in all the copper-diffused samples. The occurrence of this signal could not be correlated with the presence of the levels at Ev+0.23, Ev+0.42, or Ec−0.16 eV; this leaves the center at Ev+0.09 eV as the likely origin of the signal.

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Role of gate oxide thickness in controlling short channel effects in polycrystalline silicon thin film transistors Appl. Phys. Lett. 95, 033507 (2009);

Hot carrier instabilities in poly-Si thin film transistors (TFTs) are caused by high electric fields at the drain. These high fields are determined mainly by the abruptness of the lateral n+ doping profile in the drain and the two-dimensional (2D) coupling of the x and y components of the electric field between the gate and drain. The density of trapping states in the poly-Si film, however, has a much less significant impact on the field. Further, it is shown that improving the properties of the poly-Si film tends to have an adverse affect on hot carrier stability. Consequently, it is concluded that drain field relief is essential for hot carrier stability of n-channel poly-Si TFTs. It is shown that gate overlapped lightly doped drain (GOLDD) architectures can be used to relieve the drain field without introducing series resistance. Stable TFTs have been fabricated with GOLDD, consistent with circuit operation up to drain biases of 20 V. GOLDD is also effective in reducing the field enhanced leakage current in the off-state.

Articles you may be interested inEffects of crystallization mechanism on the electrical characteristics of green continuous-wave-laser-crystallized polycrystalline silicon thin film transistors Appl. Phys. Lett. 103, 053515 (2013); 10.1063/1.4812669Role of the surface roughness in laser induced crystallization of nanostructured silicon films

Iron has been diffused into p- and n-type silicon containing various concentrations of carbon and oxygen. Apart from the established iron interstitial level and the iron-boron complex, no new centers were detected involving iron complexing with either the carbon or the oxygen. The iron-boron level was shown to dissociate by a recombination-enhanced mechanism and a deep acceptor level of this complex was detected at Ec −0.29 eV, which must be the recombination level rather than the well-established level at Ev +0.1 eV.