The photoluminescence spectra of CdSx Se1−x doped glasses were found to be strongly dependent on the pumping laser intensity. Two spectral features corresponding to two different recombination mechanisms were identified. The dynamic behavior can be explained by the competition between tunneling-mediated recombination of deeply trapped charges and direct recombination of excitons, free and shallowly trapped carriers, and nonradiative recombination. Large (>30 nm) blue shifts of both peaks were also observed as a function of the laser intensity.

The structure and the performance of a cascaded avalanche photodiode (APD) based on cascaded homojunctions are discussed. Similar to the hetero-structure superlattice APD, such a device has a lower excess noise and a higher gain at lower bias voltages than conventional APDs. In addition to the ionization ratio, several parameters also affect the device's performance.

We have grown InP by supplying precursors alternately into the reactor of a metalorganic chemical vapor deposition system. Epitaxial growth has been obtained with a substrate temperature as low as 330 °C. The growth process is mass transport limited in the temperature range of 420–580 °C. It is kinetic controlled below 400 °C. At 340 °C, we have achieved monolayer growth in each cycle, i.e., atomic layer epitaxy.

To obtain small size high speed ultraviolet sources, we studied the UV generation process and efficiency of GaN Blue LEDs. The blue and UV emissions follow a 4-level recombination model. Depending on a given pump pulse amplitude the UV to blue generation ratio increases and saturates with the increasing of pump pulse duration. High efficiency, upto 450 μ W UV power at 380 nm, can be obtained from a 1.2 mW blue LED.

We have characterized, using the interference structure in x-ray rocking curves, a single or double strained GaInP layer grown on an InP substrate. The measured GaInP layer thicknesses are 9±3 Å and 107±3 Å for the single strained layer samples and 7 Å/50 Å and 32 Å/32 Å for the double strained layer samples. The rocking curve results for the 107 Å single-barrier sample and the 7 Å/50 Å double-barrier sample agreed well with the cross-section transmission electron microscopy data and the secondary-ion mass spectrometry data. The x-ray interference structure for the single strained barrier samples indicates the existence of many half-monolayer steps within the 1×1 mm2 x-ray beam spot at each GaInP/InP interface.