Preparation of Band-Edge Modulated Semiconducting Films and Their Properties

带边调制半导体是一种新型的人工材料，其中a-Si_<1-x>N_x：H中的氮组分沿z方向沿着几乎是正弦调制的。这是第一次在我们的实验室里进行。导带和价带的边缘被调制成近似正弦函数。在大幅度调制的情况下，光学产生的电子和空穴可以位于导带的底部和价带的顶部周围，使得它们受到z = 0周围的调制电势的影响，这些调制电势由谐振子电势近似。因此，导带和价带的能量沿z方向沿着量子化。通过光学吸收光谱测量的光学带隙能量Eg对应于两个带的第一量子化能级之间的能量差。随着调制周期L的减小，Eg的观测值增加，与理论预测一致。在L100和67的样品中，我们还观察到光生吸收谱中的量子化结构，对应于弱Si-Si键中的自陷空穴到价带的光跃迁。该结构对应于价带的量子化能级。对于带边调制膜，在L30 290 A^^λ处观察到热发光，这在体膜中没有观察到。这些带边调制薄膜有望成为一种很有前途的量子电子器件新材料。

Band-edge modulated semiconductors are a new type of artificial materials, in which nitrogen composition, chi, in a-Si_<1-x>N_x : H is almost sinusoidally modulated along a direction, z. They were, for the first time, prepared in our laboratory. The edge of conduction band and valence band is modulated with an approximately sinusoidal function. In the case of large amplitude of modulation, optically created electrons and holes may be located around the bottom of the conduction band and the top of the valence band, so that they are affected by modulated potentials around z = 0, these being approximated by a harmonic oscillator potential. Thus, the energy of the conduction band and valence band is quantized along the z direction. The optical gap energy, Eg, measured by optical absorption spectra corresponds to the energy difference between the first quantized levels of both bands. With decreasing the modulation period, L, the observed value of Eg increased in agreement with a theoretical prediction. We have also observed a quantized structure in the photoinduced absorption spectra for samples with L 100 A^^ﾟ and 67 A^^ﾟ, corresponding to optical transitions of a self-trapped hole in weak Si-Si bond into the valence band. This structure corresponds to quantized levels of the valence band. For band-edge modulated films, the hot luminescence has been observed for L 30 290 A^^ﾟ, which has not been observed in bulk films. These band-edge modulated films ar expected to be a promising new material for quantum-electronic devices.