Pn Junction And Special Diodes Practice Questions

Consider a silicon p-n junction with a uniform acceptor doping concentration of $10^{17}cm^{-3}$ on the pside and a uniform donor doping concentration of $10^{16}cm^{-3}$ on the n-side. No external voltage is applied to the diode. Given: kT/q=26mV, $n_{i}=1.5\times 10^{10}cm^{-3}$ , $\varepsilon _{Si}=12\varepsilon _{0},\varepsilon _{0}=8.85\times 10^{-14}F/m,$ and $q=1.6\times 10^{-19}C$ . The charge per unit junction area (nC $cm^{-2}$ ) in the depletion region on the p-side is ___________

Consider avalanche breakdown in a silicon $p^{+}n$ junction. The n-region is uniformly doped with a donor density $N_{D}$ . Assume that breakdown occurs when the magnitude of the electric field at any point in the device becomes equal to the critical field $E_{crit}$ . Assume $E_{crit}$ to be independent of $N_{D}$ . If the built-in voltage of the $p^{+}n$ junction is much smaller than the breakdown voltage, $V_{BR}$ , the relationship between $V_{BR}$ and $N_{D}$ is given by

Consider a region of silicon devoid of electrons and holes, with an ionized donor density of $N_{d}^{+}=10^{17}cm^{-3}$ . The electric field at x= 0 is 0 V/cm and the electric field at x=L is 50 kV/cm in the positive x direction. Assume that the electric field is zero in the y and z directions at all points. Given $q=1.6\times 10^{-19}$ coulomb, $\epsilon _{0}=8.85\times 10^{-14}F/cm,\epsilon _{r}=11.7$ for silicon, the value of L in nm is ________

A region of negative differential resistance is observed in the current voltage characteristics of a silicon PN junction if

The built-in potential of an abrupt p-n junction is 0.75 V. If its junction capacitance $(C_{J})$ at a reverse bias $(V_{R})$ of 1.25 V is 5 pF, the value of $C_{J}$ (in pF) when $V_{R}$ = 7.25 V is ________.

The electric field profile in the depletion region of a p-n junction in equilibrium is shown in the figure. Which one of the following statements is NOT TRUE?

For a silicon diode with long P and N regions, the accepter and donor impurity concentrations are $1 \times 10^{17} cm^{-3}$ and $1 \times 10^{15} cm^{-3}$ , respectively. The lifetimes of electrons in P region and holes in N region are both 100 $\mu s$ . The electron and hole diffusion coefficients are $49 cm^{2}/s \; and \; 36 cm^{2}/s$ , respectively. Assume kT/q = 26 mV, the intrinsic carrier concentration is $1 \times 10^{10} cm^{-3}, \; and \; q = 1.6 \times 10^{-19}$ C. When a forward voltage of 208 mV is applied across the diode, the hole current density (in nA/ $cm^{2}$ ) injected from P region to N region is _____________.

When the optical power incident on a photodiode is 10 $\mu$ W and the responsivity is 0.8 A/W, the photocurrent generated (in $\mu$ A) is _____.

The donor and accepter impurities in an abrupt junction silicon diode are $1 \times 10^{16} cm^{-3}$ and $5 \times 10^{10}cm^{-3}$ , respectively. Assume that the intrinsic carrier concentration in silicon $n_{i}=1.5 \times 10^{10}cm^{-3}$ at 300K, $\frac{kT}{q}=26mV$ and the permittivity of silicon $\varepsilon_{st} =1.04 \times 12^{-12}F/cm$ . The built-in potential and the depletion width of the diode under thermal equilibrium conditions, respectively, are

Consider an abrupt PN junction (at T = 300 K) shown in the figure. The depletion region width $X_{n}$ on the N -side of the junction is 0.2 $\mu$ m and the permittivity of silicon ( $\varepsilon_{st}$ ) is $1.044\times 10^{-12}$ F/cm. At the junction, the approximate value of the peak electric field (in kV/cm) is_____.

In a forward biased pn junction diode, the sequence of events that best describes the mechanism of current flow is

The i-v characteristics of the diode in the circuit given below are

The current in the circuit is

A Zener diode, when used in voltage stabilization circuits, is biased in

A silicon PN junction is forward biased with a constant current at room temperature. When the temperature is increased by $10^{\circ}$ C, the forward bias voltage across the PN junction

Compared to a p-n junction with $N_{A}=N_{D}=10^{14}/cm^{3}$ , which one of the following statements is TRUE for a p-n junction with $N_{A}=N_{D}=10^{20}/cm^{3}$ ?

Consider a silicon p-n junction at room temperature having the following parameters: Doping on the n-side = $1 \times 10^{17}cm^{-3}$ Depletion width on the n-side = 0.1 $\mu$ m Depletion width on the p -side = 1.0 $\mu$ m Intrinsic carrier concentration = $1.4 \times 10^{10}cm^{-3}$ Thermal voltage = 26 mV Permittivity of free space = $8.85 \times 10^{-14}F \cdot cm^{-1}$ Dielectric constant of silicon = 12 The peak electric field in the device is

Consider the following assertions. S1 : For Zener effect to occur, a very abrupt junction is required. S2 : For quantum tunneling to occur, a very narrow energy barrier is required. Which of the following is correct ?

Which of the following is NOT associated with a p-n junction ?