3) The band gaps of AIN, GaN, InN are 6 eV, 3 eV, i eV, respectively. a. Without

Question

3) The band gaps of AIN, GaN, InN are 6 eV, 3 eV, i eV, respectively. a. Without considering the bandgaps, what about these compounds indicates that they could be extrinsic semiconductors (created not natural)? Now, considering the band gaps, describe each compound with one of the following terms conductor, semiconductor, or insulator. c. For a semiconductor in part b, what could you dope it with to make it an n-type semiconductor? d. Explain the band gap differences for the three compounds based on the degree of orbital overlap that leads to the bands and the electronegativity of each atom in each compound.

Explanation / Answer

3-a) all the compounds are made by elements of group 13 and group 15. The natural semiconductors which are germanium and silicon belongs to group 14 and has 4 electrons in their outer shell. While here in Al, Ga, In all have 3 electrons in their outer shell and nitrogen has 5 electrons in their outer shell. The nitrogen here behaves as a dono and Al, In, Ga bahaves as acceptor, accepting a electron given by donor nitrogen so as to have 4 electrons in their outer shell and behave as semiconductor.

b) As we know that conductors have a very small band gap and hence we can say that InN is a conductor, while insulators have avery high band gap and hence AlN can be assumed to be in insulator. Now, the band gap of semiconductor lies between conductor and inulator and hence GaN can be assumed as semiconductor having a band gap of 3 ev

c) the semiconductor in part B, i.e. GaN can be made n type semiconductor by doping elements of group 15 i.e. by doping nitrogen, phosphorous, arsenic, antimony, bismuth.

d) The group 13 elements i.e. Al, Ga, In increases in size as we move downwards, and also have extra shels added to them. Now, the bands which are further away from the nucleus are easier to bond and hence In bonds easily compared to Al and Ga and Ga bonds easily compared to Al. this results in lowest band energy in In and highest in AiN. Also, as Aluminium more electropositive as compared to ga ehich in turn is more electropositive as compared to in, Al have a hard time forming a bond and can not give up electrons.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.