We have measured the electroabsorption in low-temperature grown GaAs by performing room-temperature transmission experiments in the spectral range from 1.3 to 1.9 eV for different electric fields induced by a voltage applied to a metal-semiconductor-metal structure. The devices were separated from the substrate by using an epitaxial liftoff technique. Therefore, we have been able to observe the electro-optic effect at the fundamental band gap as well as at the split-off band edge. The absorption is clearly polarization dependent at the fundamental band gap but only weakly at the split-off band gap, in agreement with the theory of the Franz-Keldysh effect.
We report on investigations of the ambipolar diffusion coefficient in GaAs n-i-p structures in which the electron density in the n channel is varied. The ambipolar diffusion coefficient was determined by time-resolved diffusion experiments of the Shockley–Haynes type. The dependence of the ambipolar diffusion coefficient on the varying carrier density is in excellent agreement with the theory of ambipolar diffusion in n-i-p-i systems. In the investigated sample, the ambipolar diffusion coefficient reaches a maximum value of 16 300 cm2/s. Although the ambipolar diffusion constant declines with decreasing carrier density, it is in a wide range of the carrier density more than two orders of magnitude enhanced compared to bulk materials.
Articles you may be interested inTemperature dependence of the refractive index of direct band gap semiconductors near the absorption threshold: Application to GaAs J. Appl. Phys. 80, 4626 (1996); 10.1063/1.363445AlGaAs/GaAs quantum well heterostructures grown by the low temperature LPE technique AIP Conf.Effects of low-temperature-grown GaAs and AlGaAs on the current of a metal-insulator-semiconductor structureWe report on transmission measurements on low temperature grown GaAs and standard GaAs for a spectral range 0.8 -2.8 eV. We measured a drastic reduction of absorption due to annealing over the whole spectral range. The absorption changes depend on the annealing temperature and occur in two individual phases. Additional transmission measurements on samples without antireflection coating confirm our earlier results of an annealing induced refractive index change of ⌬nϷ0.2.
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