Photoluminescence (PL) of quantum dots embedded in high potential barriers is studied as functions of barrier thickness and temperature. With the increase of barrier thickness, both the strengthened two-dimensional electron gas (2DEG) structure and strongly localized electron wave functions can increase the carrier recombination. The optical properties of two different-barrier-thickness samples exhibit different characteristics with the decreased measurement temperatures. The PL recombination characteristic of the samples with the barriers adjacent to a Si-doping GaAs layer is different fromthat of samples with the barrier adjacent to an i-GaAs layer.

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.

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.