Synthesis and Properties of Ternary Alloy Chalcopyrite Semiconductors

VII SYNTHESIS AND PROPERTIES OF TERNARY ALLOY CHALCOPYRITE SEMICONDUCTORS 

The ternary semiconductors of the type CuInSe, AglnSe, etc. crystallize in the chalcopyrite structure whose unxt cell is compared to that of the zincblend structure in Fig. 18. 

The chalcopyrite tetragon consists essentially of two zincblend cubes it contains two metal sublattices, one for column I elements (Cu,Ag), the other for column III elements (A ,Ga,In) instead of the single metal sublattice of the zincblend structure. The x-ray diffraction pattern of the chalcopyrite structure contains the same major lines as that of the zinc blend structure but it contains additional distinctive superlattice lines. 

If we were to construct first order iso - E, isolattice constant maps based on the values shown in Table IV, we would find that the group of alloys in Table V would satisfy these criteria. This was first pointed out by the Brown University group a9,2(3 whose research we shall describe in greater detail in what follows. 

Synthesis began by preparing a mixture of ultra pure powders of the elements comprising the desired semiconductor in the appropriate weight fraction ratio. This mixture of elemental powders was sealed in evacuated silica tubes which were heated at about 35QO for about 24 hours to promote solid state interdiffusion of the elements. The temperature of the resulting sintered mass was then increased at a rate of about 25° per hour until it became molten usually this required a temperature between 700 and lOOO C. The material was left at this temperature for about 24 hours and then cooled to room temperature. The reacted material was then 

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