Optical studies are reported of multiple quantum wells, based on AlGaN for emission in the deep ultraviolet. The materials are grown using gas source molecular beam epitaxy in a growth regime which transitions from purely two-dimensional to mixed two- and three-dimensional well formation. Low temperature photoluminescence and absorption measurements are used to obtain the Stokes shift, and temperature dependence is used to estimate the thermal activation energy associated with photoluminescence intensity decrease. Variations in these energies are attributed to the well morphologies.

We studied the effect of RTP and furnace annealing on the transport properties and electroluminescence of Si-nc embedded in SiO2 layers, and of Er ions coupled to Si-nc. The light emitting devices have been fabricated in a CMOS line by implantation of Si and Er in SiO2. The results show that for the same annealing temperature, furnace annealing decreases electrical conductivity and increases probability of impact excitation, which leads to an improved external quantum efficiency. Correlations between phenomenological transport models, annealing regimes, and erbium electroluminescence are observed and discussed.

We use transient absorption methods to characterize the sequential two-photon absorption in a quantum-dot super-lattice based intermediate band solar cell (QD-IBSC). Using collinear, orthogonally polarized beams generated from an Optical Parametric Oscillator (OPO) at varying time delay, tuned stepwise from 1050nm to 1250nm, we use the solar cell photocurrent as a direct measure of the transient absorption by measuring the differential photo-current as a function of time delay between two energetically degenerate, 100fs pulses. For comparison, we measure the pulse autocorrelation in the same geometry using a GaAsP photodiode, where all observed photocurrent is derived from instantaneous two-photon absorption. Our measurements show that at high intensity, the measurement is dominated by instantaneous two photon absorption, with a simultaneous sequential two-photon photocurrent which persists beyond the pulse overlap. Our measurements demonstrate the method can reveal carrier dynamics in a working QD-IBSC, and their dependence on energy. The method could potentially give details of the band structure formed in the QD-IBSC. Such knowledge may benefit device development and future designs of IBSCs based on QD superlattices or alternative intermediate band materials or device structures.