A quantum dot (QD) can capture and emit carriers, the behavior of which is similar to that of a giant trap, and stacked QDs with a size-controlled growth show a strong tendency to align vertically. The discrete energy level properties of the self-assembled vertically stacked InAs QDs in Al0.5Ga0.5As are studied by means of deep level transient spectroscopy (DLTS) and photoluminescence (PL) spectroscopy. The DLTS measurement displays the spectra of hole and electron discrete energy levels as positive and negative peaks, respectively, which illustrates that the DLTS is a capable tool to study the optical and electrical properties of the QDs. The PL emission peaks are found to completely correspond to the DLTS signals.

Quantum dots (QDs), which capture and emit carriers like a giant trap, are studied using deep level transient spectroscopy (DLTS). The electrons and holes in the QDs are emitted from the relevant energy levels to the conduction and valence bands, respectively, of the barrier layers with increasing temperature. The thermal emission energies from the QDs are related to their initial energy levels. In this paper, five-period vertically stacked InAs QDs in the barrier layers of a field-effect type structure are measured. The results agree well with capacitance-voltage and photoluminescence measurements. In addition, the dependence of DLTS signal on the pulse voltage and light illumination is presented. The results prove that DLTS is a powerful tool for the study of the electronic structure of QDs.

An attractive feature of vertically stacked InAs/AlGaAs quantum dots (QDs), which were buried in AlGaAs high potential barrier and spacer epilayer and grown by molecular-beam epitaxy with size-controlled growth, exhibits an unknown macroscopic quantum phenomenon (i.e., phase-change splitting of the ground state). In the vertically aligned QDs, due to many-body effect and quantum-mechanical renormalization, the electron ground state splits into a series of peaks of which the intensity gradually, systematically decreases to redshift direction with a wavelength constant. By the way, energy levels of electrons and holes might really be "seen" by deep level transient spectroscopy to which the photoluminescence experiment is in an excellent agreement.

This article describes size dependent charge storage effect of the InAs nanodots in the barrier layers of Al0.5Ga0.5As/GaAs field-effect diodes. This charging effect is analyzed by a capacitance-voltage (C-V) measurement at 77 K, and results in a clockwise hysteresis loop due to the electron storage at nanodot potentials. It is revealed that the number of stored electrons is nearly independent of dot size, and the amount of stored charge increases proportionally with dot density. The retention time of the stored charge, however, is deteriorated dramatically by the inclusion of coalesced dots in the storage nodes. These C-V characteristics are in good agreement with their photoluminescence properties.

An Al0.5Ga0.5As/GaAs heterojunction field-effect transistor which consists of InAs nanodots in the barrier layer and a GaAs quantum well channel is grown by molecular beam epitaxy, and the device performance and the electron transport from the quantum well to the nanodots are studied. These InAs nanodots are grown by self-assembling in a vertically stacked form, and their optical and electrical properties are characterized by photoluminescence and capacitance-voltage measurements. The electrical injection of electrons confined at the nanodots produces a persistent electron trapping which yields a memory function in the device performance, showing a potential application for roomtemperature operation.