Abstract

The distribution of the potential and the parameters of the potential barrier for electrons in semiconductor crystallite is numerically calculated. The calculations are made in a spherical crystallite with uniformly distributed surface states and uniformly distributed donors. It is considered in the calculations that the surface charge is screened both by the ionized donors and on free electrons; the contibution of free electrons should not be neglected in semiconductors with a high concentration of free electrons. It is demonstrated that the height of the potential barrier depends non-monotonically on the concentration of the donors in the crystallite. Moreover, in the curve of the height of the potential barrier as a function of the concentration of the donors, it is possible to highlight two segments corresponding to the cases of the complete and partial depletion of the crystallite. The height of the potential barrier increases with the concentration of the donors in the first segment and decreases in the second segment. It is established that the height of the potential barrier increases with the increase in the concentration of the surface states. The possibility of the existence of surface potential barriers in nano- and polycrystalline metal-oxide semiconductors, which are applied as a sensitive layer of gas sensors, is estimated. It is concluded that if the crystallite radius in metal-oxide semiconductors does not exceed 10 nm the sensor’s sensitivity to gas could hardly be attributed to the usual barrier model. It is demonstrated that shape of crystallite and the contribution of free electrons to screening of surface charge have to be taken into account to calculation of width of potential barrier.

中文翻译：

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多晶硅和纳米晶体半导体中微晶边界处的势垒预测

摘要

数值计算了半导体微晶中电子的电位分布和势垒参数。在具有均匀分布的表面状态和均匀分布的施主的球形微晶中进行计算。在计算中考虑到，表面电荷既被电离的供体又被自由电子屏蔽。在具有高自由电子浓度的半导体中，不应忽略自由电子的竞争。已经证明，势垒的高度非单调地取决于微晶中施主的浓度。此外，在势垒高度随施主浓度变化的曲线中，可以突出显示与微晶完全和部分耗尽的情况相对应的两个段。势垒的高度随着第一段中供体的浓度增加而在第二段中减小。已经确定，势垒的高度随着表面态浓度的增加而增加。估计在用作气体传感器敏感层的纳米和多晶金属氧化物半导体中存在表面势垒的可能性。结论是，如果金属氧化物半导体中的微晶半径不超过10 nm，则传感器对气体的敏感性很难归因于通常的势垒模型。