OPTICAL AND ELECTRICAL OSCILLATIONS IN DOUBLE-HETEROJUNCTION NEGATIVEDIFFERENTIAL RESISTANCE DEVICES

The observation of optical and electrical oscillations is reported in a GaAs/AlGaAs digital optoelectronic switch (DOES) structure. The osci llations are correlated to the negative differential resistance (NDR) region typically observed in the current-voltage (I-V) characteristics of this heterostructure. Plateau-like dc I-V characteristics in the N DR region and an apparent enhancement of the dc luminescence are shown to be a direct result of device oscillations in the NDR regime. Exter nal and intrinsic circuit parameters are demonstrated to determine the temporal characteristics of both the electrical and optical oscillati ons. These oscillations can be of sufficient magnitude to induce lasin g at apparently very low dc current levels. We also show that an exter nal optical pulse can be used to reduce the extent of the NDR region a nd thereby quench optical oscillations. In this manner, an optically c ontrolled free-running optical oscillator is demonstrated.