Question

Explain the difference of an electronic state between inorganic semiconductor and organic semiconductor

Answer 1

Ans:

The electronic state or structure of an inorganic semiconductor and organic semiconductor are different. The first consequence is 'energy level'. The covalent, periodic structure of inorganic S/C results in band energy --> conduction band and valence band. In general, organic S/C don't have bands but discrete energy levels (HOMO, LUMO with respect to the bottom of valence and conduction band). Another consequence is doping effect. In inorganic S/C, atomic doping normally just increases carrier density and does not interfere the band structure. On the other hand, molecular doping in (weak Van der Waals interaction) organic S/C affects the molecular packing and assembly, hence the morphology and electronic properties of the film such as mobility, density of state distribution.

Organic semiconductors are solids whose building blocks are pi-bonded molecules or polymers made up by carbon and hydrogen atoms and – at times – heteroatoms such as nitrogen, sulfur and oxygen. They exist in form of molecular crystals or amorphous thin films. In general, they are electrical insulators, but become semiconducting when charges are either injected from appropriate electrodes, upon doping or by photoexcitation.

Where as an inorganic semiconductor made from a non-carbon based material such as silicon, gallium or arsenide. Inorganic semiconductors are used in all logic and memory chips. Contrast with organic semiconductor.