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This study is focused on the modulation response of resonant-cavity light-emitting diodes (RCLEDs). Platinum (Pt) atoms are diffused into the 660 nm RCLED epitaxial layers to increase the concentration of recombination centers and to improve the modulation speed. The RCLED has an AlInGaP multi-quantum-well active layer which was embedded into AlGaAs-distributed Bragg reflectors to form a one-wavelength (1-λ) optical resonator. Afterwards, the deep-level Pt impurity was diffused into the RCLED and an improved average rise time, from 18.07 to 12.21 ns, was obtained. The corresponding modulation frequency can be increased from 19.54 to 30.21 MHz. [ABSTRACT FROM AUTHOR]

The precipitation of arsenic in annealed Be delta-doped GaAs grown by low-temperature molecular-beam epitaxy has been studied using transmission electron microscopy. It was found that the planes doped with [Be] = 1.0 10[sup 14] cm[sup -2] always accumulate As precipitates, while the planes doped with [Be] = 1 × 10[sup 13] cm[sup -2] tend to deplete As precipitates. In contrast, the planes doped with [Be] = 3 and 2 × 10[sup 13] cm[sup -2] exhibit a weak accumulation property when annealed at 700 °C, but a depletion property when annealed 800 °C. The existence of twins and/or precipitates around the [Be]= 1.0 × 10[sup 14] cm[sup -2] doped planes found in the as-grown sample suggests a strain-induced mechanism to account for the As precipitates accumulation on these planes. [ABSTRACT FROM AUTHOR]