Which of the following can be used as an n-type dopant for silicon?

Select the correct option(s).

The intrinsic carrier concentration of a semiconductor is  at 300 K.

If the electron and hole mobilities are  and , respectively, then the intrinsic resistivity of the semiconductor (in  ) at 300 K is _________.

(Charge of an electron .)

The electron mobility  in a non-degenerate germanium semiconductor at 300 K is .

The electron diffusivity  at 300 K (in , rounded off to the nearest integer) is _________.

(Consider the Boltzmann constant  and the charge of an electron .)

For non-degenerately doped n-type silicon, which one of the following plots represents the temperature (𝑇) dependence of free electron concentration (𝑛)

A non-degenerate n-type semiconductor has  neutral dopant atoms. Its Fermi level is located at  below the conduction band  and the donor energy level  has a degeneracy of 2. Assuming the thermal voltage to be . The difference between  and  (in , rounded off to two decimal places) is __________.

The free electron concentration profile  in a doped semiconductor at equilibrium is shown in the figure, where the points , and  mark three different positions. Which of the following statements is/are true?

In a semiconductor, if the Fermi energy level lies in the conduction band, then the semiconductor is known as

For an intrinsic semiconductor at temperature , which of the following statement is true?

In an extrinsic semiconductor, the hole concentration is given to be  where  is the intrinsic carrier concentration of . The ratio of electron to hole mobility for equal hole and electron drift current is given as _________(rounded off to two decimal places).

In a semiconductor device, the Fermi-energy level is  above the valence band energy. The effective density of states in the valence band at  is . The thermal equilibrium hole concentration in silicon at  is  _________. (rounded off to two decimal places). Given KT at  is .

Consider a long rectangular bar of direct bandgap p-type semiconductor. The equilibrium hole density is  and the intrinsic carrier concentration is . Electron and hole diffusion lengths are  and , respectively. The left side of the bar  is uniformly illuminated with a laser having photon energy greater than the bandgap of the semiconductor. Excess electron-hole pairs are generated ONLY at  because of the laser. The steady state electron density at  is  due to laser illumination. Under these conditions and ignoring electric field, the closest approximation (among the given options) of the steady state electron density at , is _______.

In a non-degenerate bulk semiconductor with electron density , the value of , where  and  denote the bottom of the conduction band energy and electron Fermi level energy, respectively. Assume thermal voltage as  and the intrinsic carrier concentration is . For  3 , the closest approximation of the value of , among the given options, is _________.

Select the CORRECT statement(s) regarding semiconductor devices.

A p-type semiconductor with zero electric field is under illumination (low level injection) in steady state condition. Excess minority carrier density is zero at , where  is the diffusion length of electrons. Assume electronic charge, . The profiles of photogeneration rate of carriers and the recombination rate of excess minority carriers  are shown. Under these conditions, the magnitude of the current density due to the photo-generated electrons at  is __________  (rounded off to two decimal places).

A bar of silicon is doped with boron concentration of  and assumed to be fully ionized. It is exposed to light such that electron-hole pairs are generated throughout the volume of he bar at the rate of . If the recombination lifetime is  s intrinsic carrier concentration of silicon is  and assuming  ionization of boron, then the approximate product of steady state electron and hole concentration due to this light exposure is

The energy band diagram of a p-type semiconductor bar of length  under equilibrium condition (i.e, the Fermi energy level  is constant) is shown in the figure. The valence band  is sloped since doping is non-uniform along the bar. The difference between the energy levels of the valence band at the two edges of the bar is .

If the charge of an electron is , then the magnitude of the electric field developed inside this semiconductor bar is

A silicon  junction is shown in the figure. The doping in the P region is  and doping in the N region is . The parameters given are

Built-in voltage

Electron charge

Vacuum permittivity

Relative permittivity of silicon

The magnitude of reverse bias voltage that would completely deplete one of the two regions ( or ) prior to the other (rounded off to one decimal place) is __________ V.

A single crystal intrinsic semiconductor is at a temperature of  with effective density of states for holes twice that of electrons. The thermal voltage is . The intrinsic Fermi level is shifted from mid-bandgap energy level by

Consider the recombination process via bulk traps in a forward biased pn homojunction diode. The maximum recombination rate is . If the electron and the hole capture cross-section are equal, which one of the following is False?

A junction is made between p- Si with doping density and p Si with doping density

Given:

Boltzmann constant 

Electronic charge . Assume 100% acceptor ionization.

At room temperature (T= 300K), the magnitude of the built-in potential (in volts. correct to two decimal places) across this junction will be ________

A bar of Gallium Arsenide (GaAs) is doped with Silicon such that the Silicon atoms occupy Gallium and Arsenic in the GaAs crystal. Which one of the following statements is true?

As shown, a uniformly doped Silicon (Si) bar of length L = 0.1 µm with a donor concentration is illuminated at x = 0 such that electron and hole pairs are generated at the rate of . Hole lifetime is , electronic charge hole diffusion coefficient and low level injection condition prevails. Assuming a linearly decaying steady state excess hole concentration that goes to 0 at x = L, the magnitude of the diffusion current density at x = L/2, in, is ____________.

The dependence of drift velocity of electrons on electric field in a semiconductor is shown below. The semiconductor has a uniform electron concentration of and electronic charge . If a bias of 5 V is applied across a 1 µm region of this semiconductor, the resulting current density in this region, in , is ____________.

A small percentage of impurity is added to an intrinsic semiconductor at 300 K. Which one of the following statements is true for the energy band diagram shown in the following figure?        

The figure below shows the doping distribution in a p-type semiconductor in log scale.

The magnitude of the electric field (in kV/cm) in the semiconductor due to non uniform doping is________

Consider a silicon sample at T = 300 K, with a uniform donor density , illuminated uniformly such that the optical generation rate is  throughout the sample. The incident radiation is turned off at t = 0. Assume low-level injection to be valid and ignore surface effects. The carrier lifetimes are  and .        

The hole concentration at t=0 and the hole concentration at t = 0.3μs, respectively, are

Consider a region of silicon devoid of electrons and holes, with an ionized donor density of . The electric field at x=0 is 0 V/cm and the electric field at  is 50kV/cm in the positive x direction. Assume that the electric filed is zero in the y and z directions at all points.

Given coulomb, F/cm,   for silicon, the value of L in nm is ________.

The  I-V characteristics of three types of diodes at the room temperature, made of semiconductors X, Y and Z, are shown in the figure. Assume that the diodes are uniformly doped and identical in all respects except their materials. If , and  are the band gaps of X, Y and Z, respectively, the

A silicon sample is uniformly doped with donor type impurities with a concentration of . The electron and hole mobilities in the sample are  and  respectively. Assume complete ionization of impurities. The charge of an electron is . The resistivity of the sample (in Ω-cm) is ____________.

An n-type silicon sample is uniformly illuminated with light which generates  electron-hole pairs per  per second. The minority carrier lifetime in the sample is 1 µs. In the steady state, the hole concentration in the sample is approximately , where x is an integer. The value of x is ___.

A piece of silicon is doped uniformly with phosphorous with a doping concentration of . The expected value of mobility versus doping concentration for silicon assuming full dopant ionization is shown below. The charge of an electron is . The conductivity (in S ) of the silicon sample at 300 K is _______.

A dc voltage of 10 V is applied across an n-type silicon bar having a rectangular cross-section and a length of 1 cm as shown in figure. The donor doping concentration  and the mobility of electrons are  and , respectively. The average time (in µs) taken by the electrons to move from one end of the bar to other end is ________.        

The energy band diagram and the electron density profile n(x) in a semiconductor are shown in the figures. Assume that n(x) =, with α=0.1 V/cm and x expressed in cm. Given , and . The electron current density (in ) at

A silicon bar is doped with donor impurities. Given the intrinsic carrier concentration of silicon at T = 300 K is. Assuming complete impurity ionization, the equilibrium electron and hole concentrations are

Assume electronic charge ,  and electron mobility . If the concentration gradient of electrons injected into a P-type silicon sample is , the magnitude of electron diffusion current density (in ) is _________.

A thin P-type silicon sample is uniformly illuminated with light which generates excess carriers. The recombination rate is directly proportional to

At T = 300 K, the hole mobility of a semiconductor  and. The hole diffusion constant  in  is ________.

In the figure, ln  is plotted as a function of 1/T, where  is the intrinsic resistivity of silicon, T is the temperature, and the plot is almost linear.

The slope of the line can be used to estimate

Consider a silicon sample doped with donor atoms. Assume that the intrinsic carrier concentration.

If the sample is additionally doped with  acceptor atoms, the approximate number of  in the sample, at T=300 K, will be ______.

An N-type semiconductor having uniform doping is biased as shown in the figure.

If  is the lowest energy level of the conduction band,  is the highest energy level of the valence band and  is the Fermi level, which one of the following represents the energy band diagram for the biased N-type semiconductor?

Drift current in semiconductors depends upon

The silicon sample with unit cross-sectional area shown below is in thermal equilibrium. The following information is given: T=300K, electronic charge= , thermal voltage=26mV and electron mobility=

The magnitude of the electric field at  is

The silicon sample with unit cross-sectional area shown below is in thermal equilibrium. The following information is given: T=300K, electronic charge= , thermal voltage=26mV and electron mobility=

The magnitude of the electron drift current density at  is

In an n-type silicon crystal at room temperature, which of the following can have a concentration of?

The ratio of the mobility to the diffusion coefficient in a semiconductor has the units

Which of the following is true?

Silicon is doped with boron to a concentration of   atom/. Assume the intrinsic carrier concentration of silicon to be  and the value of  to be 25mV at 300 K. Compared to un-doped silicon, the Fermi level of doped silicon

The electron and hole concentrations in an intrinsic semiconductor are  per  at 300 K. Now, if acceptor impurities are introduced with a concentration of  per  (where  ), the electron concentration per  at 300 K will be

The concentration of minority carriers in an extrinsic semiconductor under equilibrium is:

Under low level injection assumption, the injected minority carrier current for an extrinsic semiconductor is essentially the

The majority carriers in an n-type semiconductor have an average drift velocity v in a direction perpendicular to a uniform magnetic field B. the electric field E induced due to Hall effect acts in the direction

A heavily doped n-type semiconductor has the following data:

Hole-electron mobility ratio        : 0.4

Doping concentration        :

Intrinsic concentration        :

The ratio of conductance of the n-type semiconductor to that of the intrinsic semiconductor of same material and at same temperature is given by

The band gap of silicon at room temperature is:

The primary reason for the widespread use of silicon in semiconductor device technology is

A silicon sample A is doped with of Boron. Another sample B of identical dimensions is doped with of Phosphorus. The ratio of electron to hole mobility is 3. The ratio of conductivity of the sample A to B is

The impurity commonly used for realizing the base region of a silicon n-p-n transistor is

The resistivity of a uniformly doped n-type silicon sample is 0.5Ω-cm. If the electron mobility  is  and the charge of an electron is  Coulomb, the donor impurity concentration  in the sample is

n-type silicon is obtained by doping silicon with

The bandgap of silicon at 300 K is

The intrinsic carrier concentration of silicon sample of 300 K is . If after doping, the number of majority carriers is , the minority carrier density is

An n-type silicon bar 0.1 cm long and 100  in cross-sectional area has a majority carrier concentration of  and the carrier mobility is  at 300K. if the charge of an electron is  coulomb, then the resistance of the bar is

The electron concentration in a sample of uniformly doped n-type silicon at 300 K varies linearly from  at x = 0 to 6x at x = 2μm. Assume a situation that electrons are supplied to keep this concentration gradient constant with time. If electronic charge is  coulombs and the diffusion constant , the current density in the silicon, if no electric field is present, is

The electron and hole concentrations in a intrinsic semiconductor are  and  respectively. When doped with a p-type material, these change to n and p, respectively. Then

A long specimen of p-type semiconductor material

The units of  are

The intrinsic carrier density at 300 K is , in silicon. For n-type silicon doped to , the equilibrium electron and hole densities are

An n-type silicon bar is doped uniformly by phosphorus atoms to a concentration. The bar has cross- section of  and length of 10 cm. It is illuminated uniformly for region  as shown in the figure is assume optical generation rate  Electron-Hole pairs per  per second, for this case. The hole lifetime and electron lifetime are equal, and equal to .

Evaluate the hole and electron diffusion currents at .

Following expressions and data can be used in this evaluation

Where ;

 coloumbs ;

The probability that an electron in a metal occupies the Fermi-level at any temperature

The drift velocity of electrons, in silicon

In a P type silicon sample, the hole concentration is . If the intrinsic carrier concentration is , the electron concentration is

In an extrinsic semiconductor if

(A) The resistivity decreases

(B) The temperature coefficient of resistivity is negative

(C) The photo conductivity is low

(1) The doping concentration is low

(2) The length of the semiconductor is reduced

(3) The band gap is high

(4) The area of cross-section of the semiconductor is increased

(5) The doping concentration is increased

A small concentration of minority carriers is injected into a homogeneous semiconductor crystal at one point. An electric field of 10 V/cm is applied across the crystal and this moves the minority carriers a distance of 1 cm in  sec. The mobility (in /volt.sec) will be

A p-type silicon sample has a higher conductivity compared to an n-type sample having the same dopant concentration. (True=1,False=0)

Consider the semiconductors A and B. The figure shows variation of lnρ with 1/T, where ρ is resistivity and T the temperature, for the two semiconductors. Choose the correct statement.

A semiconductor is irradiated with light such that carriers are uniformly generated throughout its volume. The semiconductor is n-type with  per . If the excess electron concentration in the steady state is  per  and if  [minority carrier life time] the generation rate due to irradiation

A silicon sample is uniformly doped with  phosphorous atoms/  and  boron atoms/.If all the dopants are fully ionized, the material is

An n-type silicon sample, having electron mobility = twice the hole mobility , is subjected to a steady illumination such that the electron concentration doubles from its thermal equilibrium value. As a result, the conductivity of the sample increases by a factor of