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(a) Top left panel: Vertical cross section of an ErAs:InGaAs superlattice. The lateral drift and vertical diffusion of photoexcited electrons are schematically illustrated. Top right panel: Top view of an illuminated photoconductive switch. The measurement circuitry has also been included. (b) Photocurrent as a function of the average incident laser power obtained on a set of seven superlattices of different periodicities for a bias voltage of .
(a) Setup for photocurrent autocorrelation experiments. (b) Typical autocorrelation trace for a bias voltage of and an average optical power per beam path of . The dip results from the photocurrent sub- linearity. The extracted lifetime in this case is . (c) Lifetime of photoexcited electrons as a function of the ErAs:InGaAs superlattice period . The solid line is a power-law fit with exponent 1.26: with in nanometer. Data for (solid circles) were obtained from autocorrelation experiments. The upper inset shows the measurement geometry, a typical trace and fit for sliding-contact measurements. This propagation technique was applied for the 5 and superlattices (open circles).
(a) Dark currents in the wafers of this study for a bias voltage of at 4.2, 77, 200, and . (b) Dark currents at room temperature in a voltage range suitable for terahertz applications for superlattice periods (from top to bottom) of 100, 64.3, 30, 40, 10, 20, and .
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