Schottky Diode – Working, Characteristics, Applications

什么是Schottky二极管？

Schottky二极管是一种设备，它属于金属 - 半导体连接二极管的类型。屏障二极管和低压二极管是Schottky二极管的其他名称。与PN连接二极管相比，Schottky二极管中的功率下降较低。一位名叫Walter.H.Schottky的科学家首先发现了Schottky二极管。

一般的ly, in a PN junction device, when positive type (p-type) and negative type (n-type) are joined together they form a PN junction. However, in a Schottky diode, materials like aluminum or platinum are used instead of P type semiconductors.

肖特基二极管的象征

下图显示了Schottky二极管的符号。

Working of Schottky Diode

该Schottky二极管的最重要的物理参数是它们的快速切换速率和较小的正向电压下降。它是一种金属 - 半导体交界处，没有能力在其交界处存储费用。这背后的原因是由于缺乏耗竭层。

通常，当电流流过二极管时，二极管端子上发生电压降。与正常二极管相比，Schottky二极管电压下降通常在0.15至0.45伏之间。正常的PN连接二极管的电压降在0.6至1.7伏之间。为了提高效率和输出，电压下降应低。在制造二极管时，N型半导体充当阴极，金属侧的作用是二极管的阳极。

当给出二极管电压时，电流向前方向流动。当该电流流过二极管时，二极管的整个端子将有最小的电压损耗。这种电压的损耗称为电压下降。

肖特基二极管的建设

It is made of a metal and semiconductor forming unilateral junction. Few metals like gold, silver, molybdenum, tungsten or platinum are utilized. Usually an N type semiconductor, which includes Gallium, is used. Silicon is used for low frequency operation.

Schottky二极管与温度下降直接相关。在N型半导体中，发生温度掺杂浓度的降低和增加。在半导体 - 金属连接处之间，耗尽层被称为Schottky屏障。

该障碍称为势能屏障。两种类型的Schottky障碍是纠正和非矫正类型。当金属和轻微掺杂的半导体相遇时，形成了肖特基屏障。顺便通过金属遇到重掺杂的半导体时，它形成了非校准屏障。当半导体掺杂增加时，耗竭层的宽度上升。同时，当宽度降低时，荷叶载体会穿过隧道并到达耗竭层。当掺杂水平增加时，连接不充当整流器，并且会变成欧姆接触。

在公正的条件下，积累在半导体侧的电子将具有比金属区域上存在的电子水平低。由于这个原因，电子无法跨越肖特基屏障。在正向偏置条件下，存在于N侧的电子获得更多的能量，以越过连接屏障并进入金属。因此，电子也称为热载体。因此，二极管称为热载体二极管。

肖特基二极管可以表示为一个电工实习ical equivalent circuit with typical values of the components is shown below.

The above circuit is minimized as shown below. This approximated circuit is used in many applications.

Specialties of Schottky Diode

• Due to the absence of the current flow from metal to N-type semiconductor, it acts as a unipolar device. Whereas, a PN junction diode is a bipolar device.
• The metal does not have any holes, it does not store any charge. Due to this reason, Schottky diode has the advantage to quickly switch with relatively low noise.
• 与PN二极管相比，它具有低屏障潜力。

Operation of Schottky Diode

Unbiased Schottky Diode

The free electrons present inside the n – type semiconductor will move from n – type semiconductor to a metal during the combination between metal and n – type semiconductor. This results in production of equilibrium state. When free electrons moves across the junction, it provides an extra electron to the atoms present in the atom.

因此，金属连接中存在的原子会收到额外的电子。负侧连接处的原子失去电子并成为正离子。在金属交界处，原子将获得额外的电子，并试图成为负离子。

Hence, this will result in production of positive ions at negative side and negative ions on the positive side at the metal junction. Depletion region will be formed when these positive and negative ions comes together. In unbiased Schottky diode, only less number of electrons will flow from semiconductor to metal. Other electron flow is stopped due to the built in voltage.

向前偏见的肖特基二极管

在N型半导体中，当电池的正末端连接到金属，负末端连接到N型导体时，称为正向偏置偏见的Schottky二极管。在二极管上，当施加正向偏置电压时，在金属和导体中形成更多的电子。

When a voltage greater than 0.2 volts are applied, free electrons cannot move through the junction barrier. Due to this current will flow through diode. When voltage value increases, depletion region becomes thin and disappears.

反向偏见的肖特基二极管

In the n-type semiconductor if the negative terminal of the battery is coupled to metal and positive terminal is connected to n-type conductor, it is called as Reverse biased Schottky diode. At the same time, if a reverse bias voltage is applied, the width of depletion region increases.

Therefore, the current flow stops. In the metal plate, there will be more number of excited electrons. Due to this, there will be flow of a small amount of leakage current. When reverse biased voltage increases further, current also increases due to weak barrier. When abnormal increase in bias voltage takes place, electric current also increases suddenly. A device will be damaged, when the depletion region breaks down.

V-I Characteristics of Schottky Barrier Diode

The V-I (Voltage-Current) characteristics of Schottky diode is shown in the below figure. Along the graph, the vertical line signifies the current flow and the horizontal line denotes the voltage applied across the Schottky diode. The V-I characteristics of Schottky diode is almost similar to the P-N junction diode.

Nevertheless, the forward voltage drop of Schottky diode is very low when compared to the P-N junction diode. The forward voltage drop ranges from 0.3 volts to 0.5 volts. The barrier of forward voltage drop is made of silicon. The forward voltage drop is proportional to the doping concentration of N type semiconductor. Due to high concentration of current carriers, the V-I characteristic of Schottky diode is steeper.

Schottky二极管的应用

Schottky二极管由于其性质而用于二极管整流器中的许多应用中。它们用于电压夹紧应用，以防止晶体管饱和度。由于这些设备需要快速开关，因此它用作数字设备中的Schottky TTL。由于数字计算机的性能是通过二极管的切换速度确定的，因此Schottky二极管是数字计算机的重要组件。