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It's the property of the material which allow only certain bandwidth of wavelength. Materials that exhibit this property is known as photonic crystal. In order to exhibit this property the material has to have a periodic arrangement of dielectric structures with periodicity of the order of wavelength.
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What is type 1 and type 2 semiconductors?
Type 1 Semiconductors: The bandgap of one semiconductor is completely contained in the bandgap of the other one. In double heterostructure design carriers will be confined in the smaller bandgap material. this structure is used to form barrier/quantum well in Multi quantum well lasers and LEds Type II: like Type I The bandgap of the two materials overlap but the changes in the conduction and valence bands change sign. this type of materials do not use for light emiiting application as carriers can not be confined.
What is the wavelength of GAAs with a bandgap energy 1.42eV?
see wavelength=1.24/Band gap energy this wavelength is in micrometer.so accordingly ans will be=1.24/1.42=0.873micrometer I think u had appeared in BSNL JTO. How many u attempted?? Vijay
Give some Examples of direct and indirect band gap semiconductors?
direct band gap-semiconductor in which the bottom of the conduction band and the top of the valence band occur at the momentum k=0;in the case of d.b.s. energy released during band-to-band electron recombination with a hole is converted primarily into radiation (radiant recombination); wavelength of emitted radiation is determined by the energy gap of semiconductor; examples of d.b.s. GaAs, InP, ZnS, ZnSs, CdS, CdSe etc. indirect bandgap semiconductor --semiconductor in which bottom of the conduction band does not occur at effective momentum k=0, i.e. is shifted with respect to the top of the valence band which occurs at k=0; energy released during electron recombination with a hole is converted primarily into phonon; e.g. Si, Ge, GaP, GaAsp ,Ge etc, .
Why silicon has potential barrier of 0.7?
The detailed answer would involve quantum physics, with terms such as the Fermi level, the Fermi statistics, and the band gap. In short, a band gap forms in a pure semiconductor crystal lattice, such as that of silicon or gallium arsenide, in a wide temperature range (roughly above the absolute zero and below the melting point of the solid). The bandgap just means that carriers, electrons or holes, cannot occupy energy levels within the bandgap. The bandgap for pure silicon at room temperature is about 1.1eV. In perspective, a particle at room temperature has a thermal energy of 0.026eV, so 1.1 eV is a big chunk of energy that an electron has to acquire to jump the gap. Statistics describes how much of the electron population has the probability of acquiring such energy. Above the forbidden band is called the conduction bands for electrons to roam with or without the aid of an electric field. Below the gap is called the valence band, where holes travel like a vacancy (the lack of an electron). Under the influence of an electric field, holes will have a net drift toward the negative electrode and electrons toward the positive. Introducing impurities into the pure solid will create trap levels within the band gap. That is, impurities always introduce imperfection. These trap levels act like a rest station, allowing electrons to be excited from the valence band to the conduction band (equivalent to holes being excited from the conduction band to the valence band) in two trips instead of one giant leap, from the top of the valence band to the trap, and then from the trap to the bottom of the conduction band. Introducing boron atoms to the silicon solid will create trap levels near the valence band; arsenic or phosphorus atoms will create traps near the conduction band. The introduction of impurities intentionally is called doping. Boron doping is called p-type (p stands for positive) and arsenic or phosphorus doping, n-type (n stands for negative). At room temperature, trap levels at slightly different energy levels in the bangap exist, but p-type doping creates traps near the top of the valence band and n-doping creates traps near the bottom of the conduction band. The Fermi level is the 50% energy level where half of the electron population can ideally be above and half below. The Fermi level is normally located where the trap levels are. At the absolute zero temperature, all electrons will be below the Fermi level, i.e. the valence band; all holes will be in the conduction band. At room temperature, some electrons acquire enough energy to jump the gap to occupy the bottom of the conduction band. Because of the forbidden gap, the levels that an electron can occupy are not always present in the bandgap. Technology has allowed p-doping and n-doping to happen consecutively and in adjacent regions in the silicon solid, to form a pn junction or diode junction. On the p-side, there is an excess of holes. Electrons are in abundancy on the n-side. By the theory of diffusion, excess holes like to diffuse to the n-side and excess electrons to the p-side. Diffusion is evident in real life. For example, human beings treasure a personal space. If everyone stands near the punch bowl at the party, someone will feel uncomfortable and move away from the table. Viola, diffusion ensures. However, nature is such that when too many electrons move to the p-side, the next electrons will have need more and more energy to overcome the repulsion from the electrons that have already migrated. Holes do the same. Eventually (microseconds is a long time in electronics), things will settle down. The phenomenon is called the thermal equilibrium. Equal numbers of electrons are crossing from p to n as from n to p. This reluctance to have more electrons migrating from n to p than from p to n is described as that an energy barrier has formed. This energy barrier is approximately 0.7 eV, which is the origin of the 0.7 V in the question, when converting from energy in [eV] to a voltage in [V] for one electron. The Fermi level plays a role of 0.7 eV here -- the Fermi level on the n-side has to align to the Fermi level on the p-side. Lining up the Fermi level on both p- and n-sides creates the potential barrier. Applying a positive bias to the p-side relative to the n-side will lower the potential barrier, causing a positive current -- electrons flowing from the negative terminal to the positive, while holes do the opposite. Mathematically, this phenomenon can be written as I = Io * [exp(qV/kT) - 1], the diode equation. In this equation, what is important for understanding is that I is the current the diode will conduct for a certain voltage applied, V. V assumes a positive value when the anode is biased more positive than the cathode or the pn junction is forward biased. Conversely, the diode is reverse biased. At room temperature, the term (kT/q) takes on a value of 0.026 V. The value for Io for silicon at room temperature is, let us say, 1E-12 A. Plugging the known values in the diode equation for an increasing V, we get the following pairs of (V,I) values: V [volts] I [amperes] 0 1E-12 0.1 4.58E-11 0.2 2.19E-09 0.3 1.03E-07 0.4 4.80E-06 0.5 2.25E-04 0.6 1.05E-02 0.7 4.93E-01 At a forward bias of 0.7V, the diode is basically a short circuit, meaning the electric field intensity is so high that practically any electrons near the pn junction on the n-side are swept across to the p-side. Recall that holes do the opposite. The potential barrier has been practically overcome/breached.
Why is biasing needed?
The function of BiasingA BJT (Bipolar Junction Transistor) require a voltage normally in the range of 0.7V for the internal junctions to become conductive. It is a fixed parameter of Silicon (Si) due to the amount of 1.1eV required to get electrons from the valence energy band into a conductive band. To be able jump the energy gap which is a forbidden band for electrons or to raise the Fermi energy level in the atom. The energy, whether it is electrically applied, thermally or optically, is required to be able change the state of a semiconductor from an insulator to an conductor. You can read more on "semiconductor theory" for better understanding. Then with a non-linear relationship the conductivity will increase as one increase the forward bias current through the base to emitter junction. Biasing is used for classical transistor amplifier applications. Biasing is required to have the transistor half way saturated for Class-A amplification or barely switched on for Class-B power amplifiers. If a Class-B amplifier is not biased, then the lower 0.7V of the audio or sine wave will not be amplified causing crossover distortion. When you bias it correctly, the distortions will be gone, since the entire half wave will then fit into the on state of the transistor. If a Class-A amplifier is not correctly biased, premature clipping on the positive or negative part of the wave will occur.Biasing may be used for other applications as well, such as photo transistors, internal construction of IC's such as op-amps.
What is importance of band gap in semiconductors?
bandgap has an importance role for conduction.if bandgap is max,the conduction of electron is min. and vice-versa.hence we can say that the bandgap desides the conductivity of any material(may be metal or nonmetal)
When we will hit the galactic photonic belt?
we already hit the galactic photonic belt said god the father.
What is a Photonic boom?
Checkov radiation
What is bifference between optical bandgap and semiconduct0r bandgap?
we all know that electrons,photons, phonons can excite an electron from valence band to conduction band...i think the main difference between electronic bandgap and optical bandgap is that in electonic its the energy required for an electron to move from the valence band to the conduction band.but in optical bandgap photons(packet of energy in the form of light waves) are assisting the electrons to move from valence band to conduction band.The difference between optical and electronic bandgap is more complexe actually. The optical bandgap is the one that can be measured using optical techniques (based on transmission and reflection, i.e. Tauc plot). However, this measurement does not take into account all traps you might have within the bandgap that can modify the energy required to move one charge carrier from the conduction band ans the conduction band. The electronic band gap (which is the one of interest in fine, in an integrated device) is measured under operation. Thus, for many devices (lasers, solar cells...etc.) the electronic bandgap (energy required to get the device working) can defer from the optical bandgap.
What is the Pakistani price of photonic shampoo?
300
What is the price of photonic shampoo?
300 rupees
What has the author William L Dahl written?
William L. Dahl has written: 'Photonic crystals' -- subject(s): Photonic crystals, Optoelectronic devices
What is the definition of optical and electrical bandgap?
Optical bandgap means bandgap estimated using optical means or characterization. In simple words, let a light of different energies incident on the material. The material absorbs some energies and transmits some energies (the detector measures this). The threshold energy at which the material starts absorbing light is "Optical Bandgap". In a similar manner, electrical bandgap means bandgap estimated using electrical means or characterization. Here instead of measuring what light is observed of transmitted. You make electrical contacts for the material and measure the current instead of optical absorption. The incident light is of course absorbed, and carriers (electrons and holes) are generated in proportion to absorption. We measure current (nothing but charge which is proportional to absorption) and this current too shoots up at a threshold energy i.e. electrical bandgap.
What property do you use to classify materials into three states?
Bandgap
Why we can't use silicon and germanium in laser diode?
becoz Si and Ge are indirect bandgap semiconductors. for lasing action direct bandgap semiconductors are required of the type In Ga As P
What are the indirect bandgap materials?
GaP in an indirect band gap material
What is type 1 and type 2 semiconductors?
Type 1 Semiconductors: The bandgap of one semiconductor is completely contained in the bandgap of the other one. In double heterostructure design carriers will be confined in the smaller bandgap material. this structure is used to form barrier/quantum well in Multi quantum well lasers and LEds Type II: like Type I The bandgap of the two materials overlap but the changes in the conduction and valence bands change sign. this type of materials do not use for light emiiting application as carriers can not be confined.
