The Investigation of Quantum Effects of Band-Edge Modulated Nano-Structure Noncrystalline

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The band-edge modulated a-Si, N : H films are used in this study as band-edge modulated nano--structure-noncrystalline semiconductors, which are fabricated by spatially modulating nitrogen content along a direction perpendicular to the deposited film. In this film, the bottom of conduction band and the top of valence band are spatially modulated along this direction, because the band gap is varied by nitrogen content. The optical gap energy has been confirmed to be varied by the modulation period of the film. This can be accounted for in terms of one-dimensional harmonic oscillator potential model giving the separation of the lowest quantized levels of both bands as a function of the modulation period.In this study, we have attempted observations of optical transitions between the quantized levels, using the techniques of optical absorption and photoconductivity. We have developed the optical system making enable to observe these transitions. The experiments are going on down to 11K fo … More r this purpose.The defects states and their quantum effects of the band-edge modulated a-Si, N : H films have been investigated using the electron spin resonance (ESR) technique. The observed g-values of silicon dangling bonds range between 2.0031-2.0039 in the films of modulation periods of 21-100Å. No dependence of the g-value on the modulation period has been observed. From the g-values, the magnetic centres responsible for ESR are identified by silicon dangling bonds having three back-bonds with nitrogen and having two back-bonds with nitrogen and one back-bond with silicon. These dangling bonds exist in the nitrogen-rich region. They are deep centres so that the g-value is not affected by quantum effect. The spin density is increased with decreasing the modulation period because the nitrogen-rich region becomes more disordered.The luminescence of the band-edge modulated films arises from radiative recombination of singlet excitons, triplet excitons and electron-hole pairs. The excitons are found to be more stabilized by the confinement effect of modulated potentials. Less