The basic element of most of the electronic devices has been the transistor which replaced previously existing vacuum tubes, since its invention in 1947 by John Bardeen and Walter Brattain at AT&T's Bell Labs in the United States. A Nobel Laureaute of Physics for the year 1965, "Richard Fenyman" has emphasized the potential of nanotechnology with his famous quote "There's Plenty of Room at the Bottom" made in 1959. In 1965, Gordon E. Moore, co-founder of Intel predicted that the number of components on the integrated circuit doubles every two years for at least 10 years from then. [Wiki] This trend is called Moore's law has been valid even now and is expected to continue for a couple of more years.
Transistors:
Transistors can be used either as 1) On/Off switch or 2) Amplifiers of electronic signals. Transistors are the basis of modern electronic devices which are made of integrated circuits containing billions of Transistors. According to Moore's law, the number of transistors that can be placed inexpensively on an integrated circuit has doubled approximately every two years. The trend has continued for more than half a century and is not expected to stop until 2015 or later [wiki].
The basic element of the transistor is p-n junction and metal-semiconductor junctions, is also an important element in many of the electronic devices.
Transport properties of a p-n junction diode:
The net flow of the electrons and holes in a semiconductor will generate currents. The process by which these charged particles move is called transport. Two basic transport mechanisms are usually considered in a semiconductor crystal : drift - the movement of charge due to electric fields, and diffusion - the flow of charge due to density gradients.
The single-junction devices such as pn homojunction diode, can be used to obtain rectifying current-voltage characteristics, and to form electronic switching circuits. The transistor is a multi-junction semiconductor device that, in conjunction with other circuit elements, is capable of current gain, voltage gain and signal-power gain. The transistor is therefore referred to as an active device whereas the diode is passive.
Critical device dimensions of the Transistors:
Gate Length (Lg): roughly the separation between source and drain
Oxide thickness (Tox): typically 1 nm
Junction depth (Xj): Typically less than the gate length
Desired Characteristics:
High ON current
Low OFF current
The challenges in scaling down the transistors (MOSFETs) can be found in the following web page:
http://www.ee.ic.ac.uk/fobelets/AED_MOSFETs&SCE.pdf or can be found in one of the following books:
1. Solid state electronic devices : Ben G. Streetman and Sanjay Kumar Banerjee
2. Nano electronics:
Different type of Transistor Design:
FET, MOSFET, CMOS, Tunneling FET, FinFET, All-round FET, FeFET
Tunneling FET:
Source and Drain are doped with different elements
Ref: http://www.yokoyama-gnc.jp/english/research/cmos.html
FD-SOI:
Latest Transistor design that is being used in the industry is called Fully Depleted Silicon on Insulator (FD-SOI) technology. As can be seen in the Figure, the transistor is made on a very thin Buried oxide layer, and therefore needs no doping in the channel. This gives very low leakage current, and increased variability of the transistors. More details can be found in the following video:
https://www.youtube.com/watch?v=uvV7jcpQ7UY
Electronic circuit design:
Electronic circuit design deals with two major categories of signals, Analog electric signals may take on any value within some finite range of voltage or current. Digital signals, however, can take on only a finite set of discrete levels. The most common digital signals are binary signals, which are represented by two discrete levels. Bridging these two words are the digital-to-analog and analog-to-digital conversion circuits (DAC and ADC, respectively). The DAC converts digital information into an analog voltage or current, whereas the ADC creates a digital number as its output that is proportional to an analog voltage or current.
Fourier demonstrated that complex signals can be represented as a linear combination of sinusoidal signals. Analog signal processing is applied to these signals using linear amplifiers; these modify the amplitude and phase of analog signals. Linear amplifiers do not alter the frequency content of the signal, other than changing the relative amplitudes and phases of the frequency components. Amplifiers are often classified by their frequency response into low-pass, high-pass, band-reject, and all-pass categories. Electronic circuits that are designed to amplify specific ranges of signal frequencies are usually referred to as filters.
Ferro electric materials:
DRAM storage capacitor
Micro actuator
NVFRAM memory cell
Infrared sensor
Thermal infrared switch
Power Electronics:
POWER electronics is the needed interface between an electrical source and a load. The source and load can differ in frequency, amplitude, number of phases, and voltages and currents can be converted from one form to another. Some examples of a power electronic system are a laptop charger converting 110 V ac power to 19 V dc power, a solar inverter converting 48 V dc power to 220 V ac power, an EV drive using 200 V dc battery power to drive 650 V ac motor, a three-phase motor driver in hybrid vehicle, electric rail, ship, and so on. The building blocks comprising a power electronics system are power semiconductor devices, gate drivers, and controller circuits, as shown in Fig. 1. To date, the power semiconductor components of this system have been well served by silicon based diodes and transistors (MOSFETs and insulated-gate bipolar transistors). Tremendous improvements in size, efficiency, weight, and power density of systems has resulted from the improved performance of silicon-based power semiconductor devices. However, devices based on silicon are rapidly approaching the fundamental material limits of silicon. This has resulted in a rapid expansion of efforts to develop wide-bandgap power semiconductor alternatives utilizing SiC and GaN, seeking further reduction in size and weight and increase in efficiency of power electronic systems.
Ref: http://avogy.com/wp-content/uploads/2015/08/Vertical-Power-p-n-Diodes-Based....pdf
