ExtraNotesOnCompoundSemiconductors

ExtraNotesOnCompoundSemiconductors - For III-V...

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EMS 172 – Extra Notes on Semiconductors Intrinsic Compound Semiconductors Silicon and germanium are examples of single component semiconductors. A compound semiconductor is one which is made up of two different elements. These two different elements may be in combinations of (Group III/Group IV) or (Group II/Group VI), so that the number of valence electrons adds up to eight. These materials have the zinc blende crystal structure, where each “A” atom lies at the center of a tetrahedral, bonded to four “B” atoms. The bonding is mixed covalent and ionic. All the equations derived earlier in the intrinsic semiconductor section are valid for intrinsic, compound semiconductors. The concept of a compound semiconductor is completely separate from the concept of doping of a group IV semiconductor (eg. Doping Si with small amounts of B or As). Extrinsic Compound Semiconductors The concept of doping in the compound semiconductors is equivalent to what was discussed earlier using the example of silicon.
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Unformatted text preview: For III-V semiconductors, we choose to a group II element to substitute for the Group III element to obtain a p-type semiconductor, and a group VI element to substitute for a group V element to obtain an n-type semiconductor. Interestingly, a group IV element, can act as an acceptor when it substitutes for the group IV element, or as a donor when it substitutes for the group III element. One more example of an n-type semiconductor exists. All the equations derived earlier in the extrinsic semiconductor section are valid for extrinsic, compound semiconductors. Cd As Ga As As As Ga Ga Ga As Ga As Covalent/ionic bonds p-type semiconductor p-type semiconductor Missing valence electron Ga Si Ga As As As Ga Ga Ga As Ga As Missing valence electron Ga Te Ga As As As Ga Ga Ga As Ga As n-type semiconductor Extra valence electron Ga As Ga As As As Ga Ga Ga As Ga As Covalent/ionic bonds III-V semiconductor Cd Te Cd Te Te Te Cd Cd Cd Te Cd Te Covalent/ionic bonds II-VI semiconductor...
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