The electroreflectance spectra(ER) have been measured on InxGa1-xAs film under various bias(Vbias), and they have exhibited many Franz-Keldysh Oscillations(FKOs) above band-gap energy. Their strength of field in the film can be obtained by the periods of FKOs. Due to many oscillations of FKOs, the Fast Fourier transform can be applied to separate heavy- and light-hole transitions. The relation between F and Vbias was nearly linear. FKOs were observable at a large range of photon energy(£_E). The mean free path of carriers can be estimated from the relation between £_E and F. It was compared with the range of order obtained from X-ray diffraction.

Abstracts Photoreflectance(PR) of surface-intrinsic n+ type doped GaAs has been measured for various power densities of pumping laser.The spectra exhibited many Franz-Keldysh oscillations,where by the electric field(F) can be determined from the technique of the fast fourier transform.It is known that F's determined from PR are subjected to photovoltaic effect ,but it is difficult to estimate the strength of modulating field in the PR measurements.Hence we have investigated the relation between F and modulating field by using electroreflectance to simulate PR.In this work,the relation will be confirmed by using solely PR.Here a method was devised to obtain the strength of modulating field in the PR measurements.The photo-voltage(Vs)of the pump beam can be measured directly with a lock-in amplifier by making electrical contacts on the front and rear sides of the sample.The strengh of modulation field is equal to Vs/d due to a uniform F in the undoped layer,where d is the thickness of the undoped layer.

In this work¡Awe studied the strain effects on heavy hole (hh) and light hole (lh) bands of Zn1-xMnxSe/GaAs by photoreflectance (PR) spectroscopy . The Zn1-xMnxSe epilayers were grown on GaAs substrates by the MBE technique . There is a biaxial compressive strain exist in the epilayer, due to the different lattice constants between epilayers and substrates .The biaxial strain will shift hh and lh bands and lift the hh-lh degeneracy. In our experiment ,we found that the splitting of the hh and lh transition energies is almost lineally proportional to the Mn ion concentrations. It can be ascribed to the strain in the epilayer . We have also measured the PR of Zn0.96Mn0.04Se/GaAs at various temperatures , and analyzed the transition energy of different temperatures in terms of Varshni relation.

It is known that electroreflectance (ER) of surface-intrinsic-n+ type doped GaAs has exhibited many Franz-Keldysh oscillations to enable the application of fast Fourier transform to separate the heavy and light-hole transitions. However each peak still contains two components, which belong to F+ F/2 and F- F/2 respectively, where F is the built-in field and F is the modulating field of applied voltage (Vac). In this work, we have used a larger Vac to modulate the field, and hence the peaks can be further separated. The peak belonging to heavy hole-transition and F- F/2 can be singled out to compare with Airy function-theory.