GATE EC Electronic Devices questions

Consider carrier transport in a Zener diode in the breakdown region. Which is the dominant transport mechanism for current flow in this case?

Consider the circuit shown in the Figure with $V_{i}=3 \mathrm{~V}$ and $V_{C C}=12 \mathrm{~V}$. Assume $V_{B E}=0.7 \mathrm{~V}$ and $\beta_{d c}=99$ for the BJT. Which of the following options is the correct value of the current $\boldsymbol{I}_{\boldsymbol{o}}$ ?

Consider a $\text{p-n}$ junction diode when it is forward biased with $2$ V. Which of the following is/are the correct magnitude(s) of the energy difference between quasi Fermi-levels, $E_{f n}$ in the $\text{n -side}$ and $E_{f p}$ in the $\text{p -side}?$

Figure shows the output characteristics of two different Bipolar Junction Transistors (BJT), BJT $1$ with magnitude of Early voltage $\left|V_{A 1}\right|$, and BJT $2$ with magnitude of Early voltage $\left|V_{A 2}\right|$. Which of the following options is/are correct regarding the Early voltages?

A small signal source, $V_{i}(t)=A \cos \left(10^{5} t\right)+B \sin \left(10^{7} t\right)$ is applied to a BJT circuit as shown in the Figure. Assume zero source resistance, $V_{B E}=0.7 \mathrm{~V}, \beta_{d c}=99$, Early voltage $=100 \mathrm{~V}$ and Thermal voltage $=25 \mathrm{mV}$. Effect of internal parasitic capacitances of the BJT may be …

Consider an LED based on a direct bandgap semiconductor material with energy bandgap $1.3$ eV. Given: Plank's constant, $h=6.63 \times 10^{-34} \mathrm{~J} \mathrm{~s}$ and speed of light in free space is $3 \times 10^{8} \mathrm{~m} \mathrm{~s}^{-1}$. In which of the following wavelength ranges the LED will NOT emit?

An $n$-channel MOSFET is connected as shown in the Figure. Assume $V_{T H}=1 \mathrm{~V}, V_{D D}=5 \mathrm{~V}$, and $\mu C_{o x}\left(\frac{W}{L}\right)=2 \mathrm{~mA} \mathrm{~V}^{-2}$ and neglect channel length modulation effects. The gate voltage ( $V_{G}$ ) of the $n$-channel $\text{MOSFET}$ (in Volt) is $\_\_\_\_$. (rounded off to two …

Consider that the concentration of electrons in a semiconductor bar varies linearly from $2 \times 10^{17} \mathrm{~cm}^{-3}$ at $x=1 \mu \mathrm{~m}$ to $1 \times 10^{16} \mathrm{~cm}^{-3}$ at $x=4 \mu \mathrm{~m}$ along the $x$-direction. Assume that the concentration of electrons is not varying along other directions (that is along $y$ - and …

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 $2.5 \times 10^{16} / \mathrm{m}^{3}$ at $300 \: \mathrm{K}$. If the electron and hole mobilities are $0.15 \mathrm{~m}^{2} / \mathrm{Vs}$ and $0.05 \mathrm{~m}^{2} / \mathrm{Vs}$, respectively, then the intrinsic resistivity of the semiconductor (in $\mathrm{k} \Omega . \mathrm{m}$ ) at …

The electron mobility $\mu_{\mathrm{n}}$ in a non-degenerate germanium semiconductor at $300 \: \mathrm{K}$ is $0.38 \mathrm{~m}^{2} / \mathrm{Vs}$. The electron diffusivity $D_{n}$ at $300 \: \mathrm{K}$ (in $\mathrm{cm}^{2} / \mathrm{s}$, rounded off to the nearest integer) is _________. (Consider the Boltzmann constant …

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

​​​The free electron concentration profile $n(x)$ in a doped semiconductor at equilibrium is shown in the figure, where the points $\mathrm{A}, \mathrm{B}$, and $\mathrm{C}$ mark three different positions. Which of the following statements is/are true?

Consider a MOS capacitor made with p-type silicon. It has an oxide thickness of $100 \mathrm{~nm}$, a fixed positive oxide charge of $10^{-8} \mathrm{C} / \mathrm{cm}^{2}$ at the oxide-silicon interface, and a metal work function of $4.6 \mathrm{eV}$. Assume that the relative permittivity of the oxide is 4 and the absolute permittivity of free space is …

A non-degenerate n-type semiconductor has $5 \%$ neutral dopant atoms. Its Fermi level is located at $0.25 \mathrm{eV}$ below the conduction band $\left(E_{C}\right)$ and the donor energy level $\left(E_{D}\right)$ has a degeneracy of $2$. Assuming the thermal voltage to be $20 \mathrm{mV}$, the difference between $E_{C}$ and $E_{D}$ (in …

The photocurrent of a $\text{PN}$ junction diode solar cell is $1 \mathrm{~mA}$. The voltage corresponding to its maximum power point is $0.3 \mathrm{~V}$. If the thermal voltage is $30 \mathrm{mV}$, the reverse saturation current of the diode (in $\mathrm{nA}$, rounded off to two decimal places) is $\_\_\_\_\_\_$.

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 $\text{T}=0 \; \text{K}$, which of the following statement is true?

For a $\text{MOS}$ capacitor, $\text{V}_{\mathrm{fb}}$ and $\text{V}_{\mathrm{t}}$ are the flat-band voltage and the threshold voltage, respectively. The variation of the depletion width $\left(\mathrm{W}_{\mathrm{dep}}\right)$ for varying gate voltage $\left(\text{V}_g\right)$ is best represented by

In an extrinsic semiconductor, the hole concentration is given to be $1.5 n_{i}$ where $n_{i}$ is the intrinsic carrier concentration of $1 \times 10^{10} \mathrm{~cm}^{-3}$. The ratio of electron to hole mobility for equal hole and electron drift current is given as ________ (rounded off to two decimal places).