PICOSECOND OPTICAL BISTABILITY IN ZNSE-ZNTE/CAF2 MULTIPLE QUANTUM-WELLS AT ROOM-TEMPERATURE

We present the first observation of room-temperature picosecond optical bistability in ZnSe-ZnTe multiple quantum wells (MQWs) grown by metalorganic chemical vapour deposition (MOCVD) on transparent CaF2(111) substrates. On the basis of the direction of the hysteresis loop, the absorption and the energy band structure in ZnSe-ZnTe MQWs, we show that the nonlinear mechanism for the optical bistability of ZnSe-ZnTe MQWs is due to the effect of increasing absorption, which is ascribed to the band gap shrinkage of ZnSe-ZnTe MQWs due to the high density of electrons and holes in the MQWs. The ps switching time can be explained by the electrons excited to the conduction band of ZnTe layer in ZnSe-ZnTe MQWs relaxing quickly to the conduction band of ZnSe layer in this material system.