摘要
碳化硅以其禁带宽度大，击穿电场高，热导率大，电子饱和漂移速度高等
优异特性成为继锗、硅、砷化镓之后的新一代半导体材料。本文在SiC肖特基
势垒二极管的静态伏安特性方面进行了较为深入的研究。首先，比较系统和全
面地讨论了碳化硅的晶体结构，有效载流子的多级离化模型和迁移率拟合公式，
分析了“冻析”效应，得到了碳化硅材料的迁移率以及杂质离化率随温度的变
化规律。其次，研究了室温下金属碳化硅接触的肖特基势垒高度和串联电阻
，给出了它们的计算公式。证明了在温度不太高的范围（300K—500K）内，
正向伏安特性符合热电子发射理论。提出了一种计算反向电流密度的理论模型，
模型的计算结果与实验数据的比较表明，隧道效应是常温下反向电流的主要输
运机理。但在温度较高时，反向热电子发射电流和耗尽层中复合中心产生电流
都大大增加，不能再忽略不计。最后，实际测量了Ti/4H-SiC肖特基势垒二极管，
测量结果与理论计算值符合得较好，室温下理想因子、势垒高度分别为1.3和
0.8eV左右，开启电压约为0.5V。
Silicon carbide is an attractive new generation semiconductor
material following.
Ge, Si, and GaAs due to its excellent properties such as wide
bandgap, high breakdown
field, high thermal conductivity and high saturation electron
drift velocity. In this paper,
the static I-V characteristics of Schottky barrier diodes for
silicon carbide are studied
systematically. The main points in this paper are summarized as
follows:
Firstly, the crystal structure of silicon carbide, a two-level
ionization model for
effective carriers and its fitting formulas are discussed in
detail, and the phenomena of
carrier freeze-out are studied. The temperature dependence of
electron mobility and the
impurity ionization rate are presented.
Secondly, the Schottky barrier height and series resistance under
room temperature
are analyzed, and their relative formulas are obtained. Then it
is demonstrated that the
current conduction mechanism follows the thermionic emission
theory at the
temperature range from 300K to 500K under forward biased
conditions. A theoretical
model used in calculating reverse current density is proposed
considering several
current transport mechanisms. The comparison of theoretical
results with experimental
data indicates that tunneling effect is the dominant mechanism
under room temperature,
but the thermionic emission current and the generation current in
the depletion region
will increase greatly when temperature becomes high so that they
are no longer
negligible.
Finally, the measurements of Ti/4H-SiC Schottky barrier diodes
have been done
and our models proposed in this paper are in good agreements with
the experimental
data. The ideality factor and barrier height are 1.3 and 0.8eV,
respectively.
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