Capacitance-voltage characteristics have been measured at various frequencies and temperatures for structures containing a sheet of self-assembled InAs quantum dots in both n-GaAs and p-GaAs matrices. Analysis of the capacitance-voltage characteristics shows that the deposition of 1.7 ML of InAs forms quantum dots with electron levels 80 meV below the bottom of the GaAs conduction band and two heavy-hole levels at 100 and 170 meV above the top of the GaAs valence band. The carrier energy levels agree very well with the recombination energies obtained from photoluminescence spectra. (C) 1998 American Institute of Physics. [S0003-6951(98)01034-1

We report a Raman scattering investigation of InAs vibrational modes in multiple layers of InAs self-assembled quantum dots in a GaAs matrix. The Raman peak associated with quantum-dot phonons shows a downward frequency shift as the interlayer spacing decreases. We attribute this frequency shift to the relaxation of the elastic strain in the stacked quantum-dot layers. From the phonon frequency shift, we estimate the magnitude of the strain in the quantum dot layers, which we relate to the energy of the photoluminescence emission of the dots.

The numerical self-consistent solution of the coupled Schrödinger and Poisson equations is used to simulate the C–V characteristic of Schottky barrier heterostructures with a single quantum well (SQW). This model is applied to study n-type SQW structures based on InGaAs/InAlAs. It has been shown from analysis of the C–V characteristics of a SQW structure that it is possible to extract information about the energy position of subband levels and the distribution of electron density in the QW. We have demonstrated that due to the two-dimensional distribution of electron gas in the QW the apparent concentration profile NC–V–W derived from the C–V characteristic fails to describe the free electron density distribution in the QW layer. However, the number of the NC–V–W peaks indicates the quantity of electron subband levels in the QW situated below the Fermi level at zero reverse bias.

We investigate carrier dynamics in optically excited n-i-n GaAs/(AlGa)As resonant tunneling diodes that incorporate a single layer of InAs quantum dots in the center of the GaAs quantum well (QW). Voltage-tunable resonant changes in the dot luminescence are observed and are discussed in terms of the tunneling of carriers into the resonant states of the QW and of the capture of carriers from the QW into the dots