Behavior of gold in the Si/SiO2 interface region has been investigated using deep level transient spectroscopy (DLTS) in the MOS structures made on p-type silicon wafers with orientation. The results are as follows. A new defect, Au-Hit(0.445), has been observed at the interface, which is the incorporation of gold atom by the interaction with the interface defect, Hit(0.494). A continuous spectrum of the interface states related to gold has also been measured in the lower half of Si band gap, which are acceptors, and the physical mechanism of the positive shift of the flat band voltage of the MOS structure caused by gold doping ean be explained in terms of these gap states. The profile of the gold donors in the silicon near the interface has been obtained, which is not monotonically increase towards the surface but exhibits a maximum at 0.37μm from the surface.
A minority earlier peak is discovered in the DLTS of a silicon p+n junction doped with gold under majority carrier pulse condition. The major experimental results and systematic physical analyses is presented. We show, that the minority carrier peak is a result due to the capture of a free minority carrier tail from the side of the heavily doped region of the p+n junction at the mincrirty carrier traps in the space charge region, which is built by the built-in potential, and its subsequent emission.
We have discussed the kinetics of the capturing of freemajority tail by deep centres in semeconductors. We pointout that, the DLTS' signal is dicrectly proportional to the pulse width, if the DLTS' response region is restricted in the end of free-carrier tail vegion.This phenomenon may be used to measure the majority carrier capture cross section, in which the net shallow impurity concentration and the majority carrier capture cross section are both relatively wigh.
Using the method of transient capacitance at constant temperature, the shift of gold acceptor energy level in silicon under 〈100〉,〈110〉,〈111〉 uniaxial press has been studied. Considering the split of conduction band caused by uniaxial stress, a formula for electron emission rate from deep center to conduction band has been derived. With this formula and experimental data of emission rate and reported tangential deformation potential constant Ξu ,the active energy of gold acceptor under various uniaxial stress has been determined. In the range of experimental stress (0-9 kbar), a linear dependence of active energy on stress has been found. When uniaxial presses are parallel to 〈110〉,〈111〉 crystal orientations, the proportionality constants are α=-3.2±0.6 meV/kbar, α=-0.3±0.6 meV/kbar respectively. When uniaxial press is parallel to 〈100〉 crystal orientation and if we take Ξu = 9.2 eV, α= -5.8± 0.8 meV/kbar, or if Ξu =11.4 eV, α=-5.3± 0.8 meV/kbar. The changes of active energy are strongly anis-otropic. Further more, we have determined the shift coefficients of gold acceptor level in the presence of uniaxial stress relative to the bottom of conduction band in the absence of uniaxial stress. When Ξu=9.2 eV, the coefficients are S=-1.3±0.8 meV/kbar, S=0.7±0.6 meV/kbar, S=-0.7±0.6 meV/kbar respectively, when Ξu=11.4 eV, the values are S= - 3.5± 0.8 meV/kbar, S = 0.0±0.6 meV/kbar, S=- 1.0±0.6 meV/kbar. Deviations among three coefficients of each group are larger than uncertainty of experiments. Thus, the possibility that gold centers in silicon have cubic symmetry and at the same time both negatively charged and neutral gold centers have nondegenerate basic states is quite small.
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