[1] They generally exhibit large band gaps, making them popular for short wavelength applications in optoelectronics.
In particular, III-V semiconductor compounds like gallium arsenide are frequently used as cheap substrates, resulting in stronger tensions between substrate and growth layer and (generally) lower optoelectronic properties.
Especially wide bandgap II-VI semiconductor compounds are expected to be very good candidates for high performance applications, such as light emitting diodes and laser diodes for blue and ultraviolet applications.
[3] Ternary compounds are one option to vary the band gap of semiconductors almost continuously over a wide energy range.
In particular, materials with very different lattice constants or different crystal phases (wurtzite or zincblende in this case) are difficult to combine.