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Microelectronics Journal. 01/2008; 39:7-11.
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ABSTRACT: We report on the application of the deep level transient spectroscopy technique to the study of hole emission from the confined energy levels in quantum dots. The results are presented for self-assembled InAs quantum dots grown on p-type InAlAs barrier layers, lattice matched to an InP(0 0 1) substrate. Two deep levels, linked to the quantum dots, are detected, indicative of strong hole confinement. They were attributed respectively to hole emission from the ground state to the excited state with an activation energy of about 200 meV, and from the excited state to the InAlAs valence band edge with an activation energy of about 250 meV. A mechanism for a hole emission process occurring via an excited state is proposed.
Semiconductor Science and Technology 01/2006; 21(3):311. · 1.72 Impact Factor
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ABSTRACT: Capacitance– and reverse current–voltage (C–V) measurements have been performed on a Schottky barrier structure incorporating InAs quantum dots (QDs) embedded in n-type InAlAs matrix. The electron confined energy level positions in the QDs have been deduced from a capacitance–voltage analysis. Three electron levels have been found at about 240 meV, 180 meV and 70 meV via the InAlAs conduction band edge, and were attributed to the s ground state, the first p excited state and the d state, respectively. The variation of the leakage current density as a function of the depletion layer width has revealed an additional reverse current in the plane containing the dots. It was attributed to the discharging of the InAs QDs through the InAlAs barrier. The effective generation lifetime depth profile was derived from the C–V and the reverse current–voltage measurements. The effective generation lifetime was found to be controlled by the confined states in the QDs. Electrical field effect studies lead us to suggest a mechanism of electrons injection and emission into/from the confined states in the QDs.
Semiconductor Science and Technology 04/2005; 20(6):514. · 1.72 Impact Factor
