Consider the zinc blende structure of GaAs in which the Ga atoms occupy the face
ID: 919334 • Letter: C
Question
Consider the zinc blende structure of GaAs in which the Ga atoms occupy the faces and the comers of the unit cell and As (red) atoms occupy tetrahedral sites all inside the cell. How many Ga and As atoms arc there per unit cell in GaAs? Please explain your answer. Explain why CdSnAs_2 has the same valence electron count as GaAs and thus tetrahedral bonding: Give an example of one binary (two element) compound semiconductor based on group IV elements (C, Si, Ge, Sn) that has the same structure as GaAs and explain why: List all elemental semiconductors that have the diamond structure: Indicate which are insulators semiconductors and metalsExplanation / Answer
(a). 4 Ga atoms per unit cell and 4 As atoms per unit cell.
(c). The I-VII group compounds tends to have larger band gap>3 ev then it shows higher ionicity. the incresing of cohsive energy of the crystal due to the columbic interaction between the ions favors the rock salt structure containing 6-fold coordinated atoms rather than tetrahedral bonds. binary compounds forms group IV and Vi elements such as SnS, SnSe
(d). C, Si, Ge, Sn have diamond structure
metals: Cu, Al and gold
insulators: polyethylene, polypropylene, PET, sand , SiO2
semiconductors: Si, GaAs