COMPARISON OF CALCULATED OPTICAL-RESPONSE IN CUBIC AND HEXAGONAL II-VI SEMICONDUCTORS

We calculate the dielectric function and the second-harmonic generatio n susceptibility of the II-VI semiconductors in both the cubic and hex agonal phases. These results are based on a. first-principles electron ic structure calculation using the full-potential linearized augmented plane-wave method. A comparison is made between the two phases of the linear and second-order optical response for these semiconductors by examining this response in identical coordinate reference frames. Our calculations indicate that there is little difference in the linear op tical response between the two phases of the given material below the band gap, but significant differences above the band gap. For the seco nd-order optical response there are significant differences between th e two phases of the II-VI semiconductors in both the real and imaginar y parts of this susceptibility. The physics of this behavior is discus sed. [S0163-1829(98)07035-0].