Compound Semiconductors
In addition to group IV elements, compounds of group III and group V elements, and also compounds of group II and group VI elements are often semiconductors. The common feature to all of these is that they have an average of 4 valence electrons per atom.
One example of a compound semiconductor is gallium arsenide, GaAs. In a compound semiconductor like GaAs, doping can be accomplished by slightly varying the stoichiometry, i.e., the ratio of Ga atoms to As atoms. A slight increase in the proportion of As produces n-type doping, and a slight increase in the proportion of Ga produces p-type doping.
The table below list some semiconducting elements and compounds together with their bandgaps at 300 K.
Material |
Direct / Indirect Bandgap |
Band Gap Energy at 300 K (eV) |
|
|
|
|
Groups III-V compounds |
GaAs |
Direct |
1.42 |
Groups IV-IV compounds |
α-SiC |
Indirect |
2.99 |
Groups II-VI compounds |
ZnO |
Direct |
3.35 |
Data from R.E. Hummel, Electronic Properties of Materials, 3rd edition, Appendix 4, p. 413.