Comparing The And Hetero Junctions

1638 WordsJul 9, 20167 Pages
3.1 Homo- and Hetero-junctions When the semiconductor materials are homogeneous throughout the entire structure is called a semiconductor homojunction. Materials used to form a homojunction will have similar energy bandgaps, On the other hand, when two different semiconductor materials are used to form a junction, the junction is called a semiconducror heterojunction. The hetero junction is formed with narrow bandgap material with wide bandgap material. Figure 1 shows three possible combinations. When the forbidden band gap of wide bandgap material completely overlaps the bandgap of narrow bandgap materials then it is called straddling which is applicable for most of the heterojunctions. In staggered, a fraction of wide bandgap and narrow band gap are merged tog ether. In case of broken gap there is a bandgap itself between energy bandgaps of different semiconductor. Fig.1. different types of heterojunction (a) straddling (b)staggered (c) broken gap Metal-semiconductor junction is an example of heterojunction. This junction can be created by depositing a metal such as Al or Gold or Ag over a semiconductor (ptype/n type) wafer by different deposition techniques (e-beam/thermal evaporation or sputtering/CVD). Depending on the work function of the metal, this type of junction may behave as ohmic or schottky contacts. as the name suggests if the contact is ohmic, the current –voltage relationship is linear as per Ohm’s law. For ohmic contact it is mandatory that the

More about Comparing The And Hetero Junctions

Open Document