Electron transport in triangular-barriers with buried type-II quantum dots and their photodetector applications

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In triangular barrier (TB) diodes, formed by placing acceptors in the middle part of an undoped GaAs layer between a pair of n-type electrodes, electrons are normally blocked by the barrier. Electrons can flow, however, if a sufficiently high voltage is applied to offset the barrier effect. Such diodes work also as photo-detectors, as photo-generated holes get accumulated in the vicinity of acceptors and lower the barrier.In this work, we have formed by molecular beam epitaxy novel TB diodes, in which type-II GaSb quantum dots are embedded near the acceptor layer. We have shown that their detector performances are greatly improved because photo-generated holes are mostly trapped by GaSb dots and locally reduce the barrier height. We made also TB diodes in which InGaAs quantum rods are embedded across GaAs TB diodes to show that photo-responses are further enhanced, as the electron flow is allowed only through the rods and greatly affected by photo-holes trapped in the rods.