Franz—Keldysh oscillations

Figure 2. Room tanpeiature CER and reflectance spectrum of AIGaWGaN heterostracture (a) and the analysis of Franz-Keldysh oscillation (b).

The E0 transition in GaAs is the simplest single transition that can be investigated within the III/V materials and a detailed quantitative fit has been attempted to the data of Fig. 29. A careful analysis of these data lead to the fit shown in Fig. 17 and it is clear that all the features of the experimental spectrum can be reproduced with some precision provided that the manufacturer s acceptor density be taken as the basis for the analysis. By comparing the changes in the Franz-Keldysh oscillation near 820 nm with those calculated using the intermediate field model with a presumed parabolic decay of potential inside the semiconductor depletion layer, it is found that some 70 10% of the potential is dropped inside the depletion layer of this n-type material, as can be seen in Fig. 30, and there is no evidence for the phenomenon described in the previous paragraph whereby the band... 

The PR spectra are shown in Fig. 4. We define from the Franz-Keldysh oscillation (FKO) [8] that the electric field in the GaN layer of the sample A is larger than in B (about 470 kV/cm vs 270 kV/cm). This fact is caused by the larger stress in the GaN layer of the sample A in comparison with the sample B. We assume that namely the strain provides the worse optical properties of the sample A, since strain-related dislocations serve as nonradiative centers for nonequilibrium carriers and deteriorate the efficiency of light emission. The... 

As discussed above, surface fields do not play as important a role in the photochemistry of these systems. The electric field gradients are not generally sufficient to completely separate the electron and hole wavefunctions. In the event of surface charging, the field effects are better treated as a perturbation on the wavefunctions and can be modelled as a first-order Stark effect. The effect is similar to a Franz-Keldysh effect for bulk semiconductors except that there is still significant hole and electron wavefunction overlap. The oscillator strength remains similar in magnitude, albeit the frequency shifts to the red as the electron-hole pair is more... 

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