Optical and electrical oscillations in double-heterojunction negative differential resistance devices

The observation of optical and electrical oscillations is reported in a GaAs/AlGaAs digital optoelectronic switch (DOES) structure. The oscillations are correlated to the negative differential resistance (NDR) region typically observed in the current-voltage (I-V) characteristics of this heterostructure. Plateaulike DC I-V characteristics in the NDR region and an apparent enhancement of the DC luminescence are shown to be a direct result of device oscillations in the NDR regime. External and intrinsic circuit parameters are demonstrated to determine the temporal characteristics of both the electrical and optical oscillations. These oscillations can be of sufficient magnitude to induce lasing at apparently very low DC current levels. It is shown that an external optical pulse can be used to induce the extent of the NDR region and thereby quench optical oscillations. In this manner, an optically controlled free-running optical oscillator is demonstrated.<
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