Following are semiconductor materials arrange them in ascending order of their band gaps : (a) Si (b) Ge (c) Ga N (d) Ga As The correct sequence in ascending order is given by
(b), (a), (d), (c)
The four values at 300 K — worth committing to memory:
| Material | Eg (eV) | Type | Typical use |
|---|---|---|---|
| Ge (b) | 0.67 | indirect | early transistors, IR detectors |
| Si (a) | 1.12 | indirect | almost all ICs |
| GaAs (d) | 1.42 | direct | microwave devices, IR LEDs, lasers |
| GaN (c) | 3.4 | direct | blue/UV LEDs, power devices |
Ascending order:
\(Ge \lt Si \lt GaAs \lt GaN \Rightarrow (b),\,(a),\,(d),\,(c)\)
The physical trend behind the numbers. Band gap reflects bond strength. Going down a group the atoms grow larger, the bonds weaken and Eg falls — hence germanium below silicon. Compounds of group III with group V have a partly ionic bond, which is stronger than a purely covalent one, so they sit higher; and within them the gap widens as the atoms get smaller and more electronegative, which is why the nitride GaN towers over the arsenide GaAs.
What each value buys.
A small gap means many thermally generated carriers, since \(n_i\propto e^{-E_g/2kT}\) — so germanium leaks badly and is limited to about 70 °C, while silicon works to 150 °C and GaN devices operate far hotter still.
The gap also fixes the emitted wavelength through \(\lambda(\mu m)=1.24/E_g(eV)\): GaAs at 1.42 eV emits at 870 nm in the infrared, whereas GaN at 3.4 eV reaches 365 nm in the ultraviolet — which is exactly why blue and white LEDs had to wait for gallium nitride.
Hence, the ascending order of band gaps is (b), (a), (d), (c).
Similar Questions
Arrange the following in descending orders of Energy gaps of semiconductor Materials.
A. Si
B. Ge
C. GaAs
D. GaP
Choose the correct answer from the options given below :
Following semiconductor materials are given :
(a) Si
(b) Ge
(c) GaP
(d) GaAs
Arrange them in ascending order of their band gap. The correct option is :
The following materials are given, arrange them in ascending order of their band gap :
(a) Germanium (b) Carbon (diamond) (c) Silicon carbide (d) Aluminium Nitride
Important Questions from Energy Band Gap
- Which among the following represents the energy level of quantum Dot ?
Arrange the following in descending orders of Energy gaps of semiconductor Materials.
A. Si
B. Ge
C. GaAs
D. GaP
Choose the correct answer from the options given below :
Following semiconductor materials are given :
(a) Si
(b) Ge
(c) GaP
(d) GaAs
Arrange them in ascending order of their band gap. The correct option 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 $E_{gX}$, $E_{gY}$ and $E_{gZ}$ are the band gaps of X, Y and Z, respectively, then
An electron in the conduction band
