Excitonic electroabsorption spectra and Franz-Keldysh effect ofIn0.53Ga0.47As

Abstract

The influence of electric fields on excitons and band states of a bulk semiconductor grown lattice matched to an n-InP substrate is studied by measuring absorption and differential electroabsorption spectra, i.e., by weak modulation of static fields. At small fields, field broadening of light-and heavy-hole excitons, split by residual strain, determines the shape of the electroabsorption spectrum. At slightly larger fields Franz-Keldysh oscillations of the band states develop, the discrete exciton lines disappear in the absorption spectrum and their electroabsorption signal becomes part of the response of the continuum. The transition from excitonic electroabsorption to the Franz-Keldysh effect is clearly resolved and both regimes are compared with theoretical models. The observable range of Franz-Keldysh oscillations increases linearly with the field which corresponds to a constant mean free path of free carriers of 160 nm and to a collision rate that increases with the square root of energy. Different reduced mass of light-and heavy-hole transitions leads to beat in the spectrum. For static fields above 10 kV/cm the electroabsorption spectra, in particular, the decay of the amplitude with increasing energy, is quantitatively described by the one-electron theory if an energy-dependent scattering rate accounts for a field-independent mean free path. ͓S0163-1829͑98͒04639-6͔

Comparative electroabsorption studies of organic and inorganic solids

“…The broadening of the oscillations scales to F 2=3 which yields the field in the sample (Eq. (2)) and the amplitude of the signal agree with the prediction of the Franz-Keldysh effect once the finite coherence length of an excited pair is included [8]. The range of oscillations increases linearly with the field and corresponds to the energy gained by acceleration until scattering destroys the coherence of the excited pair [10].…”

“…(1) with the exciton radius a B as mean displacement r jk and the binding energy as energy denominator. Perturbation theory fails in InGaAs for fields near 2 kV/cm due to a large dielectric constant, e % 13; and a small reduced mass (m n ¼ 0:038m 0 ) so that the absorption changes are observed in static fields [8]. Fig.…”

Study of semiconductor surfaces and interfaces using electromodulation

“…Jaeger et al 43 and Pollak et al 44 have extracted a 'coherence' length (L c ) of the electron-hole pair from the FKOs observed in EM. This length can be defined on the following basis…”

Stark effect and Franz-Keldysh effect of a quantum wire realized by conjugated polymer chains of a diacetylene 3NPh2

“…[37][38][39][40] The gradual transition from the Stark e¤ect of a bound exciton to …eld ionization has been observed in cubic semiconductors. 27 The excitonic signal changes its lineshape to that of a …eld-broadened state which joins the continuum when the …eld-induced potential across the exciton radius is about half the amplitude. The negative EA peak at 3.122 eV is smaller by a factor 3 which points to a smaller radius of about 40 Å.…”