What is the hall voltage for intrinsic semiconductor?
Before coming to the answer.First,we understand what is Hall voltage?The Hall effect is the production of avoltage difference (the Hall voltage) across an electrical conductor, transverse to an electric current in the conductor and a magnetic field perpendicular to the current.The hall voltage is across the two opposite sides of block (Front and Back).Now,for an intrinsic semiconductor the concentration of holes and electron are equal.So from Lorentz force equation both the holes and electron carriers start deflecting towards the back face(considering forward face as +Y axis).Resulting in a neutral surface,thus no potential between the opposite faces.Zero Hall voltage .Well,fell in a trap.This is not the real story.Let start again.The equation representing Hall VoltageVH= IB/conductivty*×distance bw two facesThus clearly the hall volatage depends on conductivity .But wait conductivity depends on mobility of charge carrier.Does it point on something.Yes, electrons has higher mobility than holes.It means intrinsic semiconductor will behave as an ntype semiconductor.Problem solved . the hall voltage effect is negative.
Which shows stronger Hall effect: metallic conductors or semiconductors?
Semiconductors !When a current carrying semiconductor is placed in a magnetic field, the charge carriers experience force in the direction which is perpendicular to the flow of current and magnetic field, which results in development of voltage in the edges of semiconductor, which is the hall effect i.e., the production of voltage difference!Reason:As conductivity is inversely proportional to Hall Voltage ,and we know that semiconductors have lesser conductivity than metals . So, semiconductors show high hall voltage as compared to metals . thereby showing stronger Hall effect !
What is the effect of temperature on an intrinsic semiconductor?
The main effect of temperature on an intrinsic semiconductor is that resistivity decreases with an increase in temperature. This is because heating increases the concentration of electrons and holes because electron/hole pairs are thermally generated at a higher rate. Another way of saying this is that heating breaks bonds between silicon atom; each broken bond results in the creation of a free electron and a hole. This effect is exponential with temperature.A secondary effect which would increase resistivity, the decrease in mobility of electrons and holes with temperature, is much weaker than the generation effect. The secondary effect is also found in metals where it is the main effect. This is why the opposite effect in semiconductors was a “surprise” when first discovered.Apart from resistivity there are other temperature effects. Heating will also expand the semiconductor (whether intrinsic or not) and will change the band gap slightly. Both of these effects are small and barely noticeable with crude experiments.
How does the Hall effect work for semiconductors?
when a current carrying semiconductor is placed in a magnetic field, the charge carriers experience force in the direction which is perpendicular to the flow of current and magnetic field, which results in development of voltage in the edges of semiconductor, which is the hall effect i.e., the production of voltage difference
In intrinsic semiconductor. Why is current due to both electrons and holes, when holes are formed due to absence of these electrons?
Actually in intrinsic semiconductors holes are created due to the lattice imperfections or there may be other reasons(like lattice vibrations, heat transfer etc). But lets tell that none of them are present except lattice imperfections. These lattice imperfections; however do not affect the semiconductor as the electron doesn’t leave the atom, hence the atom will stay neutral electrically. Now moving onto the answer, if an electron is misplaced anyhow from its location then there will be a positive charge. (It must be noted that there is not actually any positive charge, but as electron has left the place, there is a void in which one more electron can be placed. So the hole will behave as if it has a positive charge.) Now when we give potential difference to the semiconductor, some of the electrons will take place in such holes and they may also place off other electrons by colliding with it , creating more holes. Now when electron moves through the circuit you will see that some of the holes are filling with incoming electrons while some electrons are knocked off and had created another hole. So the whole scenario will look like the holes are also moving along with the motion of electrons. Hence it is said that electrons and holes both are responsible in creating the current in semiconductor. However it must be mept in mind that holes are not really holes but as there are no electrons, it is imagined that there are holes. Holes are purely hypothetical, there is not any physical charge in it.
How does the Hall effect show whether holes or electrons are predominant in a semiconductor?
The Hall effect is the “pile up” of charge carriers on one side or the other due to the presence of a magnetic field. Magnetic field causes moving charges to move in an arc and not the normal straight line of just an electric field.Imagine looking down on a bar of semiconductor. The bar is pointing north-south. Now imaging applying a positive voltage on the north end. Current will flow from north to south. If this current is composed of electrons then the electrons are flowing from south to north, if the current is of holes then they are flowing from north to south… you don’t know this from the current reading… how to tell?Now apply a magnetic field pointing straight at you (remember you’re looking down on the bar). This field will cause holes to deflect to the west (left) edge BUT it will also cause electrons to deflect to the west edge. One carrier type would deflect clockwise, the holes, coming from the north. The other carrier type, the electrons, would deflect counter-clockwise but they are coming from the south. (The two fields act on the two types of charges oppositely but a positive-positive effect is equivalent to a negative-negative effect.) By measuring voltage across the bar, you can tell which charges piled up. It will be a positive voltage from west to east if holes, and a negative voltage from west to east if electrons. For a picture and more physics and equations see:Marko Sokolich's answer to Why does Hall voltage have opposite polarity in p type semiconductors as opposed to n type semiconductors?
Is Titanium Dioxide a n-type or p-type semiconductor?
Experiments on titanium dioxide show that it is an electronic semi-conductor in which the the current carriers are actually free electrons, as contrasted with the hole conduction of the other type of semi-conductor. It is found that the variation with oxygen pressure is that which would be expected if the titanium dioxide decomposes in the following manner: TiO2-->Ti++O2+e-. The deviation of the curves at low pressures is probably due to the presence of small impurities in the samples used. It is found that the variation of conductivity with temperature is represented by the formula σ=Ae-ɛkT. The activation energy ɛ is about 1.7 electron volts. Transport measurements show that the ionic conductivity is less than that which can be measured in these experiments. Measurements of the Hall effect, although not very quantitative, show that the mean free path for the conduction electrons is very small. In a practical sense, TiO2 is a conductor as sputtered onto semiconductors (maybe in a highly rich O2 plasma - not sure). Al is a a conductor as well - but as a doapant in Si or Ge it a p-type dopant as it supplies only 3 3electrons and thus produces a hole -
Why intrinsic semiconductor not used in industry?
intrensic semiconductor as you know is pure (without doping). And have lower conductivity compared to conductors . So to improve conductivity doping is done. We know benefit of semiconductor is that we can control the conductivity by doping it. And in almost all practical application we need to adjust conductivity to obtain derired property hence doping is done. Hence almost exclusively extrensic semiconductor is used practically.one more thing u can say is intrensic semiconductor is a normal conductor with higher resistance.hope u got the essence of it.
What happens if number of holes is equal to number of electrons in intrinsic semiconductor?
In an intrinsic (pure,undopped) semiconductor number density of electrons and holes are always equal.At absolute zero temperature valance band is completely filled and conduction band is completely empty.The electrons have no “room” to move and intrinsic semiconductor behaves as an insulator. At sufficiently high temperature(which is here room temperature) electrons in valance band get enough thermal energy and get excited to conduction band leaving behind equal number of holes in the valance band. Now, when voltage is applied ,the electrons in conduction band are dragged towards positive terminal and with hopping motion of electrons in valance band towards positive terminal the holes are moving towards negative terminal. Both these motions cause the current in intrinsic semiconductor.In short motion of electrons in conduction band and opposite motion of holes in valance band give current in intrinsic semiconductor.
What is/are the methods used to experimentally determine the electron and hole mobilities of intrinsic semiconductors and procedures?
Electron mobility - WikipediaAs can be seen, there are a lot of solutions .