Introduction
The book is organized into five parts:
- Part I: Semiconductor Physics
- Part II: Device Building Blocks
- Part III: Transistors
- Part IV: Negative-Resistance and Power Device
- Part V: Photonic Device and Sensors
Part I, Chapter 1, is a summary of semiconductor properties that are used throughout the book as a basis for understanding and calculating device characteristics.
Energy band, carrier concentration, and transport properties are briefly surveyed, with emphasis on the two most-important semiconductor: silicon (Si) and gallium arsenide (GaAs).
A compilation of the recommended or most-accurate values for these semiconductors is given in the illustrations of Chapter 1 and in the Appendixes for convenient reference.
注：介绍半导体相关背景知识
Part II, Chapter 2 though 4, treats the basic device building blocks from which all semiconductor devices can be constructed.
Chapter 2 considers the p-n junction characteristics. Because the p-n junction is the building block of mist semiconductor devices, p-n junction theory serves as the foundation of the physics of semiconductor devices.
Chapter 2 also considers the heterojunction, that is a junction formed between two dissimilar semiconductors. For example, we can use gallium arsenide (GaAs) and aluminum arsenide (AlAs) to form a heterojunction.
The heterojunction is a key building block for high-speed and photonic devices,
Chapter 3 treats the metal-semiconductor contact, which is an intimate contact between a metal and a semiconductor.
The contact can be rectifying similar to a p-n junction if the semiconductor is moderately doped and becomes ohmic if the semiconductor is very heavily doped.
An ohmic contact can pass current in either direction with a negligible voltage drop and can provide the necessary connections between devices and the outside world.
Chapter 4 considers the metal-insulator-semiconductor (MIS) capacitor of which the Si-based metal-oxide-semiconductor (MOS) structure is the dominant member.
Knowledge of the surface physics associated with the MOS capacitor is important, not only for understanding MOS-related devices such as the MOSFEF and the floating-gate nonvolatile memory but also because of its relevance to the stability and reliability of all other semiconductor devices in their surface and isolation areas.
注：介绍几种基本的器件组成结构及其它们的特性，包括pn结、金属半导体接触以及MOS电容
Part III, Chapters 5 through 7, deals with the transistor family.
Chapters 5 treats the bipolar transistor, that is, the interaction between two closely coupled p-n junctions.
The bipolar transistor is one of the most-important original semiconductor devices.
The invention of the bipolar transistor in 1947 ushered in the modern electronic era.
Chapter 6 considers the MOSFET (MOS field-effect transistor). The distinction between a field-effect transistor and a potential-effect transistor (such as the bipolar transistor) is that the in the former, the channel is modulated by the gate through a capacitor whereas in the latter, the channel is controlled by a direct contact to the channel region [1].
The MOSFET is the most-important device for advanced integrated circuits, and is used extensively in microprocessors and DRAMs (dynamic random access memories).
Chapter 6 also treats the nonvolatile semiconductor memory which is the dominant memory for portable electronic systems such as the cellular phone, notebook computer, digital camera, audio and video players, and global positioning system (GPS).
Chapter 7 considers three field-effect transistors; The JFET (junction field-effect-transistor), MESFET (metal-semiconductor field-effect-transistor), MODFET (modulation-doping field-effect-transistor).
The JFET is an older member and now used mainly as power devices, whereas the MESFET and MODFET are used in high-speed, high-input-impedance amplifiers and monolithic microwave integrated circuits.
注：介绍半导体几种重要的晶体管，包括双极性晶体管、MOS晶体管等
Part IV, Chapters 8 through 11, considers negative-resistance and power devices.
In Chapter 8, we discuss the tunnel diode (a heavily doped p-n junction) and the resonant-tunneling diode (a double-barrier structure formed by multiple heterojunctions, 共振隧穿二极管).
These devices show negative differential resistances due to quantum-mechanical tunneling.
They can generate microwaves or serve as functional devices, that is, they can perform a given circuit function with a greatly reduced number of components.
Chapter 9 discusses the transit-time devices. When a p-n junction or a metal-semiconductor junction is operated in avalanche breakdown, under proper conditions we have an IMPATT diode that can generate the highest CW (continuous wave) power output of all solid-state devices at millimeter-wave frequencies (i.e., above 30GHz).
The operational characteristics of the related BARITT and TUNNETT diodes are also presented.
The transferred-electron device (TED) is considered in Chaprer 10.
Microwave oscillation can be generated by the mechanism of electron transfer from a high-mobility lower-energy valley in the conduction band to a low-mobility higher-energy valley (in momentum space), the transferred-electron effect.
Also presented are the real-space-transfer devices which are similar to TED but the electron transfer occurs between a narrow-bandgap material to adjacent wide-bandgap material in real space as opposed to momentum space.
The thyristor (晶闸管), which is basically three closely coupled p-n junctions in the form of a p-n-p-n structure, is discussed in Chapter 11.
Also considered are the MOS-controlled thyristor (a combination of MOSFET with a conventional thyristor) and the insulated-gate bipolar transistor(IGBT, a combination of MOSFET with a conventional bipolar transistor).
These devices have a wide range of power-handling and switching capability; they can handle currents from a few milliamperes to thousands of amperes and voltages above 5000 V.
注：介绍半导体的负电阻和功率器件，其中负电阻器件是利用量子隧穿效应的（共振）隧穿二极管，而功率器件主要是晶闸管，如IGBT
Part V, Chapters 12 through 14, treats photonic devices and sensors. Photonic devices can detect, generate, and convert optical energy to electric energy, or vice versa. The semiconductor light sources--light-emitting diode (LED) and laser, are discussed in Chapter 12.
The LEDs have a multitude of applications as display devices such as in electronic equipment and traffic lights, and as illuminating devices such as flashlights and automobile headlights.
Semiconductor laser are used in optical-fiber communication, video players, and ight-speed laser printing.
Various photodetectors with high quantum efficiency and high response speed are discussed in Chaper 13.
The chapter also considers the solar cell which converts optical energy to electrical energy similar to photodetector but with different emphasis and device configuration.
As the worldwide energy demand increases and the fossil-fuel supply will be exhausted soon, there is an urgent need to develop alternative energy sources. The solar cell is considered a major candidate because it can convert sunlight directly to electricity with good conversion efficiency, can provide practically everlasting power to low operating cost, and is virtually nonpolluting.
Chapter 14 considers important semiconductor sensor. A sensor is defined as a device that can detect or measure an external signal. There are basically six types of signals: electrical, optical, thermal, mechanical, magnetic, and chemical.
The sensors can provide us with information about these signals which could not otherwise be directly perceived by our senses.
Based on the definition of sensors, all traditional semiconductor devices are sensors since they have inputs and outputs and both are in electrical forms.
We considered the seneors for electrical signals in Chapter 2 through 11, and the sensors for optical in Chapter 12 and Chapter 13.
In Chapter 14, we are concerned with sensors for remaining four types of signals, i.e, thermal, mechanical, magnetic, and chemical.
注：介绍光电器件和传感器
We recommend that readers first study semiconductor physics (Part I) and the device building blocks (Part II) before moving to subsequent parts of the book. Each chapter in Part III through V deals with a major device or a related device family, and is more or less independent of the other chapters. So, readers can use the book as a reference and instructors can select chapters appropriate for their classes and in their order of reference. We have a vast literature on semiconductor device. To data, more than 300,000 papers have been published in this field, and the grand total may reach one million in the next decade. In this book, each chapter is presented is a clear and coherent fashion without heavy reliance on the original literature. However, we have an extensive listing of key papers at the end of each chapter for reference and for further reading.
REFERENCES
[1] K. K. Ng, Complete Guide to Semiconductor Devices, 2nd Ed., Wiley, New York, 2002. [LINK] [PDF]
Chapter 1
Chapter 2 p-n Junctions
- Introduction
- Depletion Region
- Current-Voltage Characteristics
- Junction Breakdown
- Transient Behavior and Noise
- Terminal Functions
- Heterojunctions
2.1 INTRODUCTION
p-n junctions are of great importance both in modern electronic applications and in understanding other semiconductor devices. The p-n junction theory serves as the foundation of the physics of semiconductor. The basic theory of current-voltage characteristics of p-n junctions was established by Schockley [1, 2]. This theory was extended by Sah, Noyce, and Schockley [3], and by Moll [4].
The basic equations presented in Chaper 1 are used to develop the ideal static and dynamic characteristic of p-n junctions. Departures from the ideal characteristics due to generation and recombination in the depletion layer, to high injection, and to series resistance effects are then discussed. Junction breakdown, especially that due to avalanche multiplication, is considered in detail, after which transient behavior and noise performance in p-n junctions are presented.
A p-n junction is a two-terminal device. Depending on the doping profile, device geometry, and biasing condition, a p-n junction can perform various terminal functions which are considered briefly in Section 2.6. The chapter closes with a discussion of an important group of devices--the heterojunctions, which are junctions formed between dissimilar semiconductors (e.g., n-type GaAs on p-type AlGaAs).
REFERENCES
[1] W. Shockley, “The Theory of p-n Junctions in Semiconductors and p-n Junction Transistors,” Bell Syst. Tech. J., 28,435 (1949). [LINK] [PDF]
[2] W. Shockley, Electrons and Holes in Semiconductors, D. Van Nostrand, Princeton, New Jersey, 1950.[PDF]
[3] C. T. Sah, R. N. Noyce, and W. Shockley, “Carrier Generation and Recombination in p-n Junction andp-n Junction Characteristics,” Proc. IRE, 45, 1228(1957). [LINK] [PDF]
[4] J. L. Moll, “The Evolution of the Theory of the Current-Voltage Characteristics of p-n Junctions,” Proc. IRE, 46, 1076(1958). [LINK] [PDF]
2.2 DEPLETION REGION
2.2.1 Abrupt Junction
Build-in Potential and Depeletion-Layer Width. When the impurity concentration in a semiconductor changers abruptly from acceptor impurities \( N_A \) to donor impurities \( N_D \), as shown in Fig. 1a, one obtains an abrupt junction. In particular, if \( N_A \gg N_D \) (or vice versa), one obtains a one-sided abrupt \( p^{+}-n \) (or \( n^{+}-p \) ) junction.
We first consider the thermal equilibrium condition, that is, one without applied voltage and current flow. From the current equation of drift and diffusion (Eq. 156a in Chapter 1), \[ J_n = 0 = q \mu_n (n \mathcal{E} + \frac{k T }{q} \frac{dn}{dx}) = \mu_n n \frac{dE_{F}}{dx} \tag{1}\] or \[ \frac{dE_F}{dx} = 0 \tag{2} \] Similarly, \[ J_p = 0 = \mu_p p \frac{dE_F}{dx}. \tag{3} \]
Thus the condition of zero net electron and hole currents requires that the Fermi level must be constant throughout the sample. The build-in potential \( \Psi_{bi} \), or diffusion potential, as shown in Fig. 1b, c, and d, is equal to \[ q \Psi_{bi} = E_{g} - (q \psi_{n} + q \psi_{p}) = q \Psi_{Bn} + q \Psi_{Bp}. \tag{4} \]
For nodegenerate semiconductors, \[ \Psi_{bi} = \frac{k T}{q} \ln(\frac{n_{n0}}{n_i}) + \frac{k T}{q} \ln(\frac{p_{p0}}{n_{i}}) \tag{5} \] \[ \approx \frac{kT}{q} \ln( \frac{N_{D} N_{A}}{ n_{i}^2} ) \]. Since at equilibrium \( n_{n0} p_{n0} = n_{p0} p_{p0} = n_{i}^2 \), \[ \Psi_{bi} = \frac{k T}{q} \ln(\frac{p_{p0}}{n_{n0}}) = \frac{k T}{q} \ln(\frac{n_{n0}}{n_{p0}}) \tag{6} \] This given the relationship between carrier densities on either side of the junction.
If one of both sides of the junction are degenerate, care has to be taken in calculating the Fermi-levels and build-in potential. Equation 4 has to be used since Boltzmann statistics cannot be used to simplify the Fermi-Dirac integral. Furthermore, incomplete ionization has to be considered, i.e., \( n_{n0} \neq N_D\) and/or \( n_{p0} \neq N_A\) (Eqs. 34 and 35 of Chapter 1).
Next, we proceed to calculate the field and potential distribution inside the depletion region. To simplify the analysis, the depletion approximation is used which assumes that the depleted charge has a box profile. Since in the thermal equilibrium the electric field in the neutral regions (far from the junction at either side) of the semiconductor must be zero, the total negative charge per unit area in the p-side must be precisely equal to the total positive charge per unit area in the n-side: \[ N_A W_{Dp} = N_D W_{Dn}. \tag{7} \] From the Poisson equation we obtain \[ -\frac{d^2 \Psi_i}{dx^2} = \frac{d \mathcal{E}}{dx} = \frac{\rho(x)}{\varepsilon_s} = \frac{q}{\varepsilon_s} [ N_D^{+}(x) - n(x) - N_A^{-}(x) + p(x)]. \tag{8}\] Inside the depletion region, \(n(x) \approx p(x) \approx 0\), and assuming complete ionization, \[ \frac{d^2 \Psi_i}{dx^2} \approx \frac{q N_A}{\varepsilon_s} \qquad \mathrm{for} \quad -W_{Dp} \leq x \leq 0, \tag{9a} \] \[ -\frac{d^2 \Psi_i}{dx^2} \approx \frac{q N_D}{\varepsilon_s} \qquad \mathrm{for} \quad 0 \leq x \leq W_{Dn} . \tag{9b} \] The electric field is then obtained by integrating the above equations, as shown in Fig. 1b: \[ \mathcal{E} = -\frac{q N_A(x + W_{Dp})}{\varepsilon_s} \qquad \mathrm{for} \quad -W_{Dp} \leq x \leq 0, \tag{10} \] \begin{align} \mathcal{E} &= -\mathcal{E_m} + \frac{q N_D x}{\varepsilon_s} \\ &= -\frac{q N_D}{\varepsilon_s}(W_{Dn} - x) \qquad \mathrm{for} \quad 0 \leq x \leq W_{Dn} \tag{11} \end{align} where \( \mathcal{E_m} \) is the maximum field that exists at \(x=0\) and is given by \[ |\mathcal{E_m} | = \frac{q N_D W_{Dn}}{\varepsilon_s} = \frac{q N_A W_{Dp}}{\varepsilon_s}. \tag{12} \] Integrating Eqs. 10 and 11 once again gives the potential distribution \(\Psi_{i}(x)\) (Fig. 1c) \[ \Psi_{i}(x) = \frac{q N_A}{2 \varepsilon_s}(x + W_{Dp})^2 \qquad \mathrm{for} \quad -W_{Dp} \leq x \leq 0, \tag{13} \] \[ \Psi_{i}(x) = \Psi_{i}(0) + \frac{q N_D}{\varepsilon_s}(W_{Dn} - \frac{x}{2})x \qquad \mathrm{for} \quad 0 \leq x \leq W_{Dn}. \tag{14} \] With these, the potentials across different regions can be found as: \begin{align} \Psi_p &= \frac{q N_A W_{Dp}^2}{2 \varepsilon_s}, \tag{15a} \ |\Psi_n| &= \frac{q N_D W_{Dn}^2}{2 \varepsilon_s}, \tag{15b} \end{align}