In this, the holes are less in number and the current due to electrons is dominant over the hole current.
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This constitutes a current and the conduction is by free electrons. When the voltage is applied to the n-type semiconductor, the free electrons which are readily available due to the included impurity move in a direction of positive terminal of the applied voltage. The pentavalent impurity has five valence electrons. N-type extrinsic semiconductor: If a small amount of pentavalent impurity is added to a semiconductor then it is called as the n-type extrinsic semiconductor.Hence this type of doping is called as acceptor doping and this result in the “p-type extrinsic semiconductor.” Examples of such materials are gallium, boron, and indium. When trivalent atoms are added to intrinsic semiconductors then it creates more holes and will be ready to accept an electron. This makes an extrinsic semiconductor with a large number of free electrons called “n-type extrinsic semiconductor.” Examples of such materials are arsenic, bismuth, and phosphorus. When pentavalent atoms are added to an intrinsic semiconductor then it is called as donor doping as each impurity atom donates one free electron to an intrinsic material and such impurity is called donor impurity. Depending upon the type of doping, the extrinsic semiconductor are two types and they are:Īlso See: Solar Mobile Charger Seminar ppt So, after the doping, the material becomes an impure or extrinsic semiconductor. Doping is nothing but the adding of a small amount of impurity to the intrinsic semiconductors. Extrinsic semiconductors: The current conduction capability should be increased by a doping process.The electrons are negatively charged particles and the holes are positively charged particles. The number of free electrons and holes are always equal in intrinsic semiconductors. The generation of the electron-hole pair due to the thermal energy is called as the thermally generated electron-hole pair. The free electrons and holes get generated in pairs.
The energy required to break the covalent bond for germanium is 0.72ev and for silicon, it is 1.1ev at room temperature. When an electric field is applied across an intrinsic semiconductor, the current conduction takes place by two processes namely the free electrons and holes. The hole also contributes to the electric current and the electron-hole pairs will be formed. A missing electron in the valence band leaves a vacant space called the hole. Under the influence of electric field, these electrons constitute an electric current. At room temperature, some of the valence electrons may acquire sufficient energy to enter the conduction band to acquire sufficient energy to enter the conduction band to form free electrons.
The diagrammatical representation of these energy gaps are explained below:Īlso See: Augmented Reality Seminar and PPT Classification of Semiconductors: In the semiconductors, the energy gap will be very small. In the conductors, the forbidden gap overlap and the energy gap will be large in the insulators.
The energy associated with forbidden band is called as energy gap and is denoted by and is measured in electron volt (eV).
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The energy bands present in the solids are as below:Īlso See: Inverter PPT | PDF | PowerPoint Presentation
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