What is the number density of donor atoms which must be added to a pure germanium semiconductor to make $n-$ type semiconductor of conductivity $6.4\ {\Omega ^{ - 1}}\,c{m^{ - 1}}$? The mobility of electr ons in $n-$ type germanium is $4 \times {10^3}\ cm^2\ V^{-1}\ s^{-1}$. Neglect the contribution of holes to conductivity
Medium
Download our app for free and get started
$\mathrm{J}=\sigma \mathrm{E}$
$\sigma=\frac{\mathrm{J}}{\mathrm{E}}=\frac{\mathrm{neVd}}{\mathrm{E}}=\mathrm{ne}\left(\frac{\mathrm{Vd}}{\mathrm{E}}\right)$
$\sigma=$ $\mathrm{ne}$ (mobility)
$6.4 \times 100\, r^{-1} m^{-1}$
$=n\left(1.6 \times 10^{-19}\right)\left(4 \times 10^{3} \times 10^{-1}\right)$
$\Rightarrow n=10^{22} \mathrm{\,m}^{-3}$
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1The $V-i$ graph for a conductor makes an angle $\theta $ with $V-$ axis. Here $ V$ denotes the voltage and $i$ denotes current. The resistance of conductor is given byView Solution
- 2$STATEMENT-1$ In a Meter Bridge experiment, null point for an unknown resistance is measured. Now, the unknown resistance is put inside an enclosure maintained at a higher temperature. The null point can be obtained at the same point as before by decreasing the value of the standard resistance. andView Solution
$STATEMENT-2$ Resistance of a metal increases with increase in temperature.
- 3View SolutionA potential difference is applied across the ends of a metallic wire. If the potential difference is doubled, then the drift velocity
- 4The figure shows three circuits $I, II$ and $III$ which are connected to a $3\,V$ battery. If the powers dissipated by the configurations $I, II$ and $III$ are $P_1 , P_2$ and $P_3$ respectively, thenView Solution
- 5In a potentiometer, the null point is received at $7^{th}$ wire. If now we have to change the null point at $9^{th}$ wire, what should we do ?View Solution
- 6A voltmeter of resistance $1000\,\Omega$ is connected across a resistance of $500\, \Omega$ in the given circuit. What will be the reading of voltmeter .............. $V$View Solution
- 7The figure shows a network of resistors and $a$ battery. If $1\,A$ current flowsthrough the branch $CF$, then answer the following questions The current throughView Solution
- 8Two cells of $e.m.f.$ $s\, E_1$ and $E_2$ and of negligible internal resistances are connected with two variable resistors as shown in Fig. When the galvanometer shows no deflection, the values of the resistances are $P$ and $Q$. What is the value of the ratio $E_2/E_1$ ?View Solution
- 9A battery having $e.m.f.$ $5\,\,V$ and internal resistance $0.5$ $\Omega$ is connected with a resistance of $4.5 \,\Omega$ then the voltage at the terminals of battery is ............. $V$View Solution
- 10Resistance of $100\, cm$ long potentiometer wire is $10 \,\Omega$, it is connected to a battery ($2\, volt$) and a resistance $R$ in series. A source of $10\, mV$ gives null point at $40\, cm$ length, then external resistance $R$ is ........... $\Omega $View Solution