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课程名称：现代物理：半导体电子器件 概述： 本课程将深入探讨半导体电子材料、器件及简单电路的基本概念。内容涵盖导体、半导体和绝缘体的能带理论、半导体二极管的I-V特性（正向和反向偏置）、以及二极管作为整流器的应用。此外，还将介绍特定用途的p-n结二极管，例如LED、光电二极管、太阳能电池和齐纳二极管及其特性，齐纳二极管作为电压调节器的应用。课程还将讲解结型晶体管、晶体管的工作原理、特性及作为放大器的应用（共发射极配置），以及模拟信号和数字信号的基本概念，包括逻辑门（OR、AND、NOT、NAND和NOR）。 课程要点： 1. 半导体是现代固态电子器件（如二极管、晶体管和集成电路）的基础材料。 2. 构成元素的晶格结构和原子结构决定材料是绝缘体、金属还是半导体。 3. 半导体可以是元素型（如Si、Ge）或化合物型（如GaAs、CdS）。 4. 纯半导体称为“内在半导体”，其电荷载流子（电子和空穴）是材料的“内在”特性，通过热激发获得。内在导体中，电子数（ne）与空穴数（nh）相等，空穴为带有有效正电荷的电子缺陷。 5. 通过掺杂适当的杂质，可以改变载流子的数量，掺杂后的半导体称为外在半导体，分为n型和p型。 6. n型半导体的电子数远大于空穴数，反之p型半导体则为空穴数远大于电子数。 7. n型半导体通过掺入五价原子（施主如As、Sb、P等）制得，而p型半导体则通过掺入三价原子（接受者如B、Al、In等）制得。 8. 半导体内存在两个不同的能带（价带和导带），价带的能量低于导带。导带的电子可自由移动并负责导电性，导电程度受价带顶部和导带底部之间的能量间隙（Eg）影响。 9. p-n结是所有半导体器件的“关键”，形成的耗尽层导致结电位屏障。 10. 通过改变外加电压，可调节结屏障。在正向偏置下，屏障减小；在反向偏置下，屏障增大，因此p-n结二极管的正向电流（mA）较大，而反向电流（µA）极小。 11. 二极管可用于整流交流电（限制交流电的方向），通过电容器或适当的滤波器可获得直流电压。 12. 齐纳二极管为特殊用途二极管，在反向偏置时，在特定电压下，电流突然增加（击穿电压），可用于电压调节。 13. p-n结还被用于多种光电器件：光电二极管通过光子激发导致反向饱和电流变化，以测量光强；太阳能电池将光子能量转化为电能；发光二极管和二极管激光器通过偏压激发产生光。 14. 晶体管是n-p-n或p-n-p结器件，中心电极称为“基极”，其他电极为“发射极”和“集电极”。发射极与基极接正偏，集电极与基极接反偏。 15. 晶体管可作为放大器和振荡器；振荡器亦可视为自激放大器。 16. 当晶体管处于截止或饱和状态时，它充当开关。 17. 一些特殊电路处理包含0和1水平的数字数据，这构成了数字电子学的内容。 18. 执行特殊逻辑操作的重要数字电路称为逻辑门，包括OR、AND、NOT、NAND和NOR门。 19. 在现代电路中，许多逻辑门或电路集成在一个“芯片”中，称为集成电路（IC）。 本课程为学习现代半导体技术奠定了理论基础，适合希望深入理解半导体电子器件的学生与专业人士。
Semiconductor Electronics: Materials, Devices and Simple CircuitsEnergy bands in conductors, semiconductors and insulators (qualitative ideas only)Semiconductor diode - I-V characteristics in forward and reverse bias, diode as a rectifierSpecial purpose p-n junction diodes: LED, photodiode, solar cell and Zener diode and their characteristics, zener diode as a voltage regulatorJunction transistor, transistor action, characteristics of a transistor and transistor as an amplifier (common emitter configuration), basic idea of analog and digital signals, Logic gates (OR, AND, NOT, NAND and NOR).SUMMARY1. Semiconductors are the basic materials used in the present solid state electronic devices like diode, transistor, ICs, etc. 2. Lattice structure and the atomic structure of constituent elements decide whether a particular material will be insulator, metal or semiconductor. 3. Semiconductors are elemental (Si, Ge) as well as compound (GaAs, CdS, etc.). 4. Pure semiconductors are called ‘intrinsic semiconductors'. The presence of charge carriers (electrons and holes) is an ‘intrinsic' property of the material and these are obtained as a result of thermal excitation. The number of electrons (ne ) is equal to the number of holes (nh ) in intrinsic conductors. Holes are essentially electron vacancies with an effective positive charge. 5. The number of charge carriers can be changed by ‘doping' of a suitable impurity in pure semiconductors. Such semiconductors are known as extrinsic semiconductors. These are of two types (n-type and p-type). 6. In n-type semiconductors, ne >> nh while in p-type semiconductors nh >> ne. 8. n-type semiconducting Si or Ge is obtained by doping with pentavalent atoms (donors) like As, Sb, P, etc., while p-type Si or Ge can be obtained by doping with trivalent atom (acceptors) like B, Al, In etc.7. There are two distinct band of energies (called valence band and conduction band) in which the electrons in a material lie. Valence band energies are low as compared to conduction band energies. All energy levels in the valence band are filled while energy levels in the conduction band may be fully empty or partially filled. The electrons in the conduction band are free to move in a solid and are responsible for the conductivity. The extent of conductivity depends upon the energy gap (Eg ) between the top of valence band (EV ) and the bottom of the conduction band EC. The electrons from valence band can be excited by heat, light or electrical energy to the conduction band and thus, produce a change in the current flowing in a semiconductor. 8. For insulators Eg > 3 eV, for semiconductors Eg is 0.2 eV to 3 eV, while for metals Eg ≈ 0. 9. p-n junction is the ‘key' to all semiconductor devices. When such a junction is made, a ‘depletion layer' is formed consisting of immobile ion-cores devoid of their electrons or holes. This is responsible for a junction potential barrier. 10. By changing the external applied voltage, junction barriers can be changed. In forward bias (n-side is connected to negative terminal of the battery and p-side is connected to the positive), the barrier is decreased while the barrier increases in reverse bias. Hence, forward bias current is more (mA) while it is very small (µA) in a p-n junction diode. 11. Diodes can be used for rectifying an ac voltage (restricting the ac voltage to one direction). With the help of a capacitor or a suitable filter, a dc voltage can be obtained. 15. There are some special purpose diodes.12. Zener diode is one such special purpose diode. In reverse bias, after a certain voltage, the current suddenly increases (breakdown voltage) in a Zener diode. This property has been used to obtain voltage regulation. 13. p-n junctions have also been used to obtain many photonic or optoelectronic devices where one of the participating entity is ‘photon': (a) Photodiodes in which photon excitation results in a change of reverse saturation current which helps us to measure light intensity; (b) Solar cells which convert photon energy into electricity; (c) Light Emitting Diode and Diode Laser in which electron excitation by a bias voltage results in the generation of light. 14. Transistor is an n-p-n or p-n-p junction device. The central block (thin and lightly doped) is called ‘Base' while the other electrodes are ‘Emitter' and ‘Collectors'. The emitter-base junction is forward biased while collector-base junction is reverse biased.15. Transistor can be used as an amplifier and oscillator. In fact, an oscillator can also be considered as a self-sustained amplifier in which a part of output is fed-back to the input in the same phase (positive feed back).16. When the transistor is used in the cutoff or saturation state, it acts as a switch. 17. There are some special circuits which handle the digital data consisting of 0 and 1 levels. This forms the subject of Digital Electronics.18. The important digital circuits performing special logic operations are called logic gates. These are: OR, AND, NOT, NAND, and NOR gates. 19. In modern day circuit, many logical gates or circuits are integrated in one single ‘Chip'. These are known as Intgrated circuits (IC).
