Comparison of bowing behaviors between III-V and II-VI common-cation semiconductor ternary alloys

The scope of the present investigation is to make a clear contrast between the bandgap bowing characters of III-V and II-VI compound-semiconductor common-cation ternary alloys. For this aim, both the sp ³ s ^- tight-binding method, with the inclusion of spin-orbit coupling, and the full-potential linear augmented plane-wave technique are used to calculate the partial and total densities of states, the constituent ionicity, and the total electron charge density for the common-cation GaSb _x As _1-x and CdSe _x Te _1-x ternary alloys. The results show that the bowing is sensitive to competition between the anions for trapping/losing electric charges. The lack of this competition would result in complete absence of the bowing, as is the case for common-anion ternary alloys. In the common-cation ternary alloys studied herein, the bowing is found to be proportional to the electronegativity of the anions χ ^anion (i.e., the 6-valency anions are more electronegative than the 5-valency ones, and consequently the former result in stronger intercompetition and yield stronger bowing in the II-VI alloys) and also proportional to the relative mismatch in electronegativity between the competing anions (δX ^anion/X _ave ^anion). The excellent agreement between our theoretical results and recent photoluminescence data corroborates our claim.