Abstract
Optical absorption edges at 300 K and 80 K have been measured for single crystals of the compounds ZnSiP2, ZnSiP1.5As0.5, ZnSiP1As1, ZnSiP0.5As1.5 and ZnSiAs2. Exponential absorption edge tails were observed in all cases. The minimum energy gap increases from ZnSiAs2 through the range to ZnSiP2; a value of approximately 2.0 eV at 300 K for ZnSiAs2 agrees with previous results, but the value of approximately 2.5 eV for ZnSiP2 is significantly higher than previous measurements.