The fourth plateaulike region of the characteristics of the SL measured at 77.3 K: (a) the characteristic observed by oscilloscope using an external sinusoidal sweep with a frequency of 1 kHz and a peak-to-peak amplitude of 1.5 V. It is visible that in the structureless regions the current oscillations are present; (b) the dc characteristic; the solid and dashed lines show the sweep-up and sweep-down curves, respectively. The fixed voltages, at which self-oscillations were studied, are shown by arrows. The frequency-voltage dependence is shown by rectangular points in the upper part of this graph.
Typical traces of the natural oscillations detected at three fixed voltages of 2.65 V (a), 2.71 V (b), and 2.83 V (c). On the right-hand panels, the Fourier spectra of these oscillations are shown.
The amplitude dependence of the first to six harmonics of the current oscillations as a function of the external driving voltage . The driving frequencies are indicated in each graph. The dependences shown by circles, squares and triangles were obtained for fixed voltages of 2.65, 2.71, and 2.83 V, respectively. The arrow indicates the threshold driving voltage at which the fundamental mode is quenched. In graph (a) for , the dashed line demonstrates that curves shown by circles and triangles can be approximated by the linear dependence.
Typical trace of the driven current oscillations detected at fixed voltage of 2.65 V by using unipolar driving voltage of negative (a) and positive (b) polarities. The driving amplitude and frequency were 35 mV and 2.03 MHz, respectively. The frequency spectra of these oscillations are shown on the right-hand panels.
Energetic diagram of the region of the domain boundary formation in the SL with two energy levels in QWs. The solid line shows that the leading edge of the domain boundary locates in the 17th period of the SL. The dashed line shows the response of the energetic structure to the carrier capture in QWs that leads to the domain boundary expansion over three SL periods. The equivalent RTD scheme is presented in the upper right inset.
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