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电材专业英语课文翻译
Semiconductor Materials
?
1.1 Energy
Bands and Carrier Concentration
?
1.1.1
Semiconductor Materials
?
Solid-state materials can be grouped
into three classes
—
insulator
s(
绝缘
体
）
,
semiconductors,
and
conductors.
Figure
1-1
shows
the
electrical
conductivities
δ
(and
the
corresponding
resistivities
ρ
≡<
/p>
1/
δ
)associated
with(
相关）
some important materials in each of
three classes. Insulators such
as
fused
（熔融）
quartz
and glass have very low conductivities, in the
order of
1E-18 to 1E-8 S/cm;
固态材
料可分为三种：
绝缘体、
半导体和导体。
图
1
－
1
给出了在三种材料中一
些重要材料相关的电阻值（相应电导率
ρ
≡
1/
δ
)<
/p>
。绝缘体如熔融石英和玻璃具
有很低电导率，在
< br>10-18
到
10-8 S/cm;
and conductors such as aluminum and
silver have high conductivities, typically from
104 to 106 S/cm. Semiconductors have
conductivities between those of insulators and
those of conductors. The
conductivity of
a semiconductor is generally sensitive
to
temperature,
illumination
（照射）
, magnetic field, and minute amount of
impurity
atoms.
This
sensitivity
in
conductivity
makes
the
semiconductor
one
of
the
most
important materials for
electronic applications.
导体如铝和银有高的电导率，<
/p>
典型值从
104
到
106S/cm;
而半导体具有的电导率介
乎于两者之间。<
/p>
半导体的电导率一般对温度、
光照、
磁场
和小的杂质原子非常敏
感。在电导率上的敏感变化使得半导体材料称为在电学应用上为最
重要的材料。
The
study
of
semiconductor
materials
began
in
early
nineteenth
century.
Over
the
years
many semiconductors have been investigated. Table
1 show a portion
（部分
) of
the
periodic(
周期）
table
related
to
semiconductors.
The
element
semiconductors,
those composed of single species of
atoms, such as silicon (Si) and germanium (Ge),
can
be
found
in
Column
Ⅳ
.
However,
numerous
compound
semiconductors
are
composed of two or more elements. For
example, gallium arsenide (GaAs) is a
Ⅲ
-
Ⅴ
compound
that
is
a
combination
（合成）
of
gallium
(Ga)
from
Column
Ⅲ
and
arsenic (As) from Column
Ⅴ
.
早在
19
世纪人们已经开始研究半导体材料。
多年来人们研究了很多半导体材料。
表
1
给出了与半导体相关的周期表中的部分元素。
由单种元素组成的单质半导体
如硅和锗在第Ⅳ族。而大量的化合物半导体有两个甚至更多元素组成。如
GaAs
是Ⅲ
-
Ⅴ化合物是由Ⅲ族的<
/p>
Ga
和Ⅴ族的
As
化合而得。
Prior to the
invention of the bipolar
transistor
（
双极二极管）
in 1947,semiconductors
were
used only as two-
terminal
（电极）
devices, such as
rectifiers
（整流器）
and
photodiodes
（<
/p>
光
敏
二
极
管
）
.
In
the
early
1950s,
germanium
was
the
major
semiconductor
material.
在
1947<
/p>
年双极晶体管发明之前，半导体仅用作双极型器件如整流器和光敏二极
管。早在
20
世纪
50
年代，锗是主要的半导体材料。
However,
germanium
proved
unsuitable
in
many
applications
because
germanium
devices
exhibited
high
leakage
currents
（漏电流）
at
only
moderately
elevated
temperatures. In addition, germanium
oxide is water soluble and unsuited for device
fabrication. Since the early 1960s
silicon has become a practical
substitute
（实际取
代）
and has now virtually
supplanted
（事实上替代）
germanium as a material for
semiconductor
fabrication(
结构）
然
而锗不太适合在很多方面应用因为温度适当提高后锗器件会产生高的漏电流。
另外，
锗的氧化物是水溶性的不适合器件制作。
所以
20
世纪
60
年代实际上锗被
硅所取代，事实上硅替代锗成为半导体制作的材料之一。
The
main
reasons
we
now
use
silicon
are
that
silicon
devices
exhibit
much
lower
leakage
currents,
and
high-quality
silicon
dioxide
can
be
grown
thermally.
There
is
also an
economic consideration. Device grade silicon costs
much less than any other
semiconductor
material. silicon in the form of silica and
silicates
（
硅酸盐）
comprises
25% of the Earth’s
crust
（地表）
, and silicon is
second only to oxygen in
abundance
（分布）
. At present,
silicon is one of the most studied elements in the
periodic table;
and
silicon
technology
is
by
far
the
most
advanced
among
all
semiconductor
technologies
我们用硅材料的主要原因有硅器件
存在非常低的漏电流且能够通过热法生长出
高质量的二氧化硅。
器件级硅成本远少于其它半导体材料。
硅以硅石和硅酸盐形
式存
在并占地球地表层的
25
％，而且硅元素在分布中排在氧之后的
第二位。当
今硅是在元素周期表中研究最多的元素；硅技术是在所有半导体技术中最先进
的。
Many of the
compound semiconductors have electrical and
optical properties that are
absent
（
缺少）
in
silicon. These semiconductors, especially gallium
arsenide (GaAs),
are use mainly for
microwave and photonic applications. Although we
do not know as
much
about
the
technology
of
compound
semiconductor
as
we
do
about
that
of
silicon,
compound
semiconductor
technology
has
advanced
partly
because
of
the
advances
in
silicon
technology.
In
this
book
we
are
concerned
mainly
with
device
physics and
processing technology of silicon and gallium
arsenide.
有很多化合物半导体具有硅所缺少的电
光性能。
这些半导体特别是
GaAs
主
要用
作微波和光学应用。
虽然我们了解化合物半导体技术不如硅
材料的多，
但化合物
半导体技术由于硅技术的发展而发展。
在本书中我们主要介绍硅和砷化镓的器件
物理和制备技术。
Crystal Structure
The
semiconductor
materials
we
will
study
are
single
crystals,
that
is,
the
atoms are
arranged in a three-dimensional periodic fashion.
The periodic arrangement
（排布）
of atoms in a crystal is called a
lattice
（晶格）
. In a crystal,
an atom never
stray
（偏离）
far from a single, fixed position. The
thermal vibrations associated with
the
atom are centered about this position. For a given
semiconductor, there is a unit
cell
（晶胞）
that
is
representative
of
the
entire
lattice;
by
repeating
the
unit
cell
throughout the crystal, one can
generate the entire lattice.
我们研究的半导体材料
是单晶，
也就是说，
原子是按照三维周期形式排列。
在晶
体中原子的周期排列称为晶格。
在晶体里，<
/p>
一个原子从不远离它确定位置。
与原
子相
关的热运动也是围绕在其位置附近。
对于给定的半导体，
存在代
表整个晶格
的晶胞，通过在晶体中重复晶胞组成晶格。
Figure 1-2 shows some
basic cubic-crystal unit cells. Figure 1-2(a)
shows a simple
cubic
（
立方）
crystal;
each corner of the cubic lattice is occupied by an
atom that has
six
equidistant
（等距）
nearest
neighboring
atoms.
The
dimension
a
is
called
the
lattice constant. Only
polonium
（钋）
is
crystallized in the simple cubic lattice. Figure
1-2(b) is a body-centered
cubic
（体心立方）
(bcc)
crystal, where in addition to the
eight
corner atoms, an atom is located at center of the
cube.
图
1
< br>－
2
给出一些立方晶体晶胞。图
1
－
2
（
a<
/p>
）给出了一个简单的立方晶体；立
方晶格的每个角由一个原子占据
，
所以有
6
个等距原子。
a
的大小称为晶格常数。
只有金属钋明确是单立方晶
体。图
1
－
2
（
b
）是体心立方晶体，除了
8
个角原子
外，一个原子在其立方中心上。
In a bcc lattice, each
atom
has
eight
nearest-
neighboring atoms. Crystals
exhibiting
bcc lattices include those of
sodium
（钨）
and
tungsten
（钠）
. Figure
1-2(c)shows a
face-centered cubic (fcc)
（面心立方）
crystal that has one
atom at each of the six
cubic faces in
addition to
（
还有）
the eight corner atoms. In an fcc
lattice, each atom
has 12 nearest neighboring atoms. A
large number of elements exhibit the fcc lattice
form, including aluminum, copper, gold,
and platinum
（铂）
.
在体心立方晶格中，每个原子具有
8
个相近原子。呈
bcc
晶格的晶体包括钨和
钠晶体。图
1
－
2
（
c
）给出了面心立方晶体除了
8
个角原子外六个立方面上还有
一个原子。在
fcc
晶格中每个原子有
12
相邻原子。大量的元素是
fcc
晶格形式，
< br>包括铝、铜、金和铂。
The element
semiconductors, silicon and germanium, have a
diamond lattice
structure
（金刚石晶体结构）
. This
structure also belongs to the cubic-crystal family
and can
be seen as two
interpenetrating
（渗透）
fcc
sublattices(
亚点阵）
with one sublattice
displaced
（移动）
from the other by one quarter of the
distance along a
diagonal
（对
角线）
of the cube (i.e.,a
displacement
（位移）
of a
3
).
/
4
元素半导体如硅和锗具有金刚石晶体结构。
< br>这种结构属于金刚石结构并且视为两
个互相贯穿的
fcc
亚点阵结构，这个结构具有一个可以从其它沿立方对角线距离
的
四分之一处移动的子晶格（位移
3
/
4
。
）
All
atoms are identical in a diamond lattice, and each
atom in the diamond lattice is
surrounded by four
equidistant
（等距）
nearest neighbors that lie at the
corners of a
tetrahedron
（四面体）
.
Most
of
the
Ⅲ
-
Ⅴ
compound
semiconductors
(e.g.,GaAs)
have a
zincblende
（闪锌矿）
lattice, which is
identical
（相同）
to
a diamond lattice
except that one fcc
sublattice has column
Ⅲ
atoms (Ga) and the other has Column
Ⅴ
atoms (As).
在金刚石晶体所有原子都相同，
且在金刚石晶体都有在四面体角上的四
个等距相
近原子所包围。多数每个原子Ⅲ
-
Ⅴ
化合物半导体具有闪锌矿结构，它有金刚石
相同结构除了一个
fcc
子晶格结构有一个Ⅲ
族原子
Ga
和
Ⅴ族原子
As
。
?
Therefore,
the
crystal
properties
along
different
planes
are
different,
and
the
electrical
and
other
device
characteristic
are
dependent
on
the
crystal
orientation. A
convenient method of defining the various planes
in a crystal is
to use Miller
indices
（密勒指数）
.
因此
，
不同面的晶体特性也不同，
且电和其它器件特性依赖于晶体取
向。
一种常
用定义在晶体中不同晶面的方法是用密勒指数。
Valence Bonds
（价键）
As
discussed
in
Section
1.1.2,
each
atom
in
a
diamond
lattice
is
surrounded by four
nearest neighbors. Each atom has four electrons in
the out orbit
（轨道）
, and each
atom shares these valence
electrons
（价电子）
with its neighbors.
This
sharing of electrons is known as covalent
bonding
（共价键）
; each electron
pair
（电子对）
constitutes a covalent bond. Covalent
bonding occurs between atoms of
the
same element, or between atoms of different
elements that have similar outer-shell
electron
configurations
（结构）
. Each
electron spends an equal amount of time with
each nucleus.
<
/p>
如
1.1.2
节所述，在金刚石结构的每
个原子被
4
个相邻原子所包围。每个原子在
外轨道具有
4
个电子，
并且每个电
子与相邻原子共享价电子；
每对电子组成一个
共价键。
共价键存在于同种原子之间或具有相同外层电子机构的不同元素的原子
间
。每个电子与每个原子核达到平衡需要相同时间。
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