A. An impurity scattering cause decrease in mobility with decrease in temperature. B. A slow moving carrier is likely to scatter more strongly than carrier with great momentum C. Drift velocity of an electron increases with decrease in mobility D. Drift velocity of an electron decrease with decrease in mobility E. At critical electric field ($=10^5V/cm$) drift velocity tends to saturate. Choose the correct answer from the options given below:
The question asks to identify the correct statements regarding carrier transport properties in semiconductors.
Analyzing Carrier Scattering and Mobility
Let's evaluate each statement:
- Statement A: Impurity scattering becomes more dominant as temperature decreases. This increased scattering impedes carrier movement, thus causing mobility ($\mu$) to decrease with decreasing temperature. Hence, statement A is correct.
- Statement B: Slower moving carriers (lower momentum) interact with scattering centers (like impurities) for a longer duration compared to faster carriers. This extended interaction leads to stronger scattering effects. Hence, statement B is correct.
- Statement C: The relationship between drift velocity ($v_d$), mobility ($\mu$), and electric field ($E$) is given by $v_d = \mu E$. If mobility ($\mu$) decreases (assuming constant $E$), drift velocity ($v_d$) must also decrease. Therefore, drift velocity does not increase with decreasing mobility. Hence, statement C is incorrect.
- Statement D: Using the equation $v_d = \mu E$, if mobility ($\mu$) decreases, and the electric field ($E$) is held constant, the drift velocity ($v_d$) will consequently decrease. Hence, statement D is correct.
- Statement E: At sufficiently high electric fields, known as the critical field (often around $10^5$ V/cm for many semiconductors), the drift velocity of carriers ceases to increase proportionally with the field and tends to saturate due to mechanisms like optical phonon scattering. Hence, statement E is correct.
Conclusion on Correct Statements
Based on the analysis, statements A, B, D, and E are correct, while statement C is incorrect.
The correct option includes A, B, D, and E only.
Important Questions from Carriers in Semiconductors
In a pure silicon, what is the time for an electron to drift $1\mu m$ in an electric field of 100 V/cm?
Assume electron mobility of $1350 \text{ cm}^2/V-s$
An n-type GaAs Gunn diode has the following parameters drift velocity (Vd) = $10^7$ cm/s, Doping concentration = $2 \times 10^{14}$ cm$^{-3}$, and electric field = 3200 V/cm. Choose the correct option:
A. Current density = 320 A/cm²
B. Electron mobility = 3100 cm²/v-s
C. Current density = 120 A/cm²
D. Electron mobility = 1450 cm²/v-s
E. Electron mobility = 1500 cm²/v-s
Choose the correct answer from the options given below:
Consider the following statements :
If an electric field is applied to an n-type semiconductor bar, the electrons and holes move in opposite directions due to their opposite charges. The net current is
1. due to both electrons and holes with electrons as majority carriers.
2. the sum of electron and hole currents.
3. the difference between electron and hole current.Which of these statements is/are correct ?
Consider the following :
1. In semiconductors, the mobility of electrons is more than that of holes.
2. In semiconductors, the resistivity increases with the increase in temperature.
3. Metal has positive TCR.
4. In metals, thermal conductivity is inversely proportional to electronic conductivity at a particular temperature.Which of the following statements are correct ?
The Debye length is a characteristic length for semiconductor. Arrange the doping density given below in such a way that Debye length changes from maximum to minimum.
(A) N = 1015 cm–3
(B) N = 1017 cm–3
(C) N = 3 × 1015 cm–3
(D) N = 1016 cm–3
(E) N = 5 × 1016 cm–3Choose the most appropriate answer from the options given below :
