Scanning electron micrograph of device and measurement setup	(a,b) Electron accumulation and (c,d) hole accumulation near quantum dot

 　　

Energy Distribution Measurement of Nonequilibrium Carriers Using a Quantum Dot

　

The quantized energy levels of electrons in a semiconductor quantum dot (QD) can be easily tuned by controlling the gate voltage, thus enabling us to use a QD as a high-resolution energy analyzer (or spectrometer) for the electrons near the QD. We used this feature of QDs to measure the energy distribution of ballistic nonequilibrium electrons and holes emitted from a quantum wire. Nonequilibrium carriers were emitted by applying a bias voltage (Vpc) to a quantum point contact. The emitted current was again focused by applying a perpendicular magnetic field (B⊥) and analyzed with a QD. When the energy of the nonequilibrium carriers coincides with the quantized energy levels, those carriers can resonantly tunnel through the QD and can be detected as an electric current. (Page 31)

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