Electronic properties and microhardness of semiconductor alloys

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Title: Electronic properties and microhardness of semiconductor alloys
Author: Ekpenuma, Sylvester Nwabuzor
Abstract: The results of theoretical investigations of the properties of semiconductor alloys are presented . First , the effects of alloy disorder on the electronic properties of four III -V quaternary alloys are investigated using an extension of the bonding -antibonding coherent potential approximation (CPA ) formalism . The alloys considered have two disordered sublattices so that their chemical formulae have the general form AxBi _a ;CyDi _y . Some alloys of this type are used in optoelectronic devices . Results are presented for the densities of states , the self energies , and the band gap bowing for the alloys Ala .Gai _a .AsyPi _y , AliGai _xAsySbi _y , Gaa :Ini _a :AsyPi _y , and Gaa .Ini _a :AsySbi _y . Comparisons of these CPA results are made with Virtual Crystal Approximation (VGA ) results , and with experimental data where available . Second , the electronic properties of the II -VI alloy Hgi _a . _yCda .ZnyTe are calculated . To do this , an extension is made of a previously developed CPA formalism for quaternary alloys of the form Ai _a . _yBa ;CyD to include spin -orbit coupling in the input bandstructures . This study is motivated by recent results that indicate improvement in the structural properties of the widely used infrared material Hgi _a .Cda .Te on the addition of few per cent zinc . Results for the effective masses and band gap variations with compositions are presented . Lastly , a formalism for the calculation of the alloy microstructural hardness is developed . This formalism combines a solid -solution hardening model , an analysis of the composition dependence of critical stress , and an empirical relation for the alloy hardness . Results for the hardness variations with composition for the II -VI alloys Cdi _a ;Zna :Te , Hgi _a .Cda .Te , Hgi _a ;ZnxTe , and Hgi _a ; _yCda ;ZnyTe are presented and compared with available data . The results for Hgi _a : -yCda ;ZnyTe verify improved structural properties of Hgi _a :Cda .Te on the addition of zinc . Results for the composition dependence of hardness are also presented for the III -V alloys InxGai _a ;As , Gaa ;Ini _a .Sb , Ala .Ini _a :Sb , Gaa ;Ini _a ;P , and Ala ;Ini _a .As and compared with experimental data where available .
URI: http : / /hdl .handle .net /2346 /9573
Date: 1990-05


Ekpenuma, Sylvester Nwabuzor Electronic properties and microhardness of semiconductor alloys. Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /9573 .

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