Instability of photoexcited electron-hole plasma in short semiconductor structures

The instability of the electron-hole plasma produced by continuous photoexcitation in short semiconductor structures is investigated theoretically. The applied electric field is considerably disturbed by photogenerated charge carriers. At a sufficiently intensive photogeneration plasma instability occurs. The frequency of current oscillations due to the instability, as shown by numerical simulation for a GaAs structure, is in the range of 10¹¹–10¹²s^–1.     

Surface phase transitions of silicon in the presence of a dense electron-hole plasma

A thermodynamic equation is given, that relates the surface phase transitions with phonon-defect- electron interactions. It permits the calculation of the variation of the phase transition temperatures, T_c, with the density of an electron-hole plasma in silicon. Under conditions met in short-pulse laser irradiation, it is shown that T_c might differ from thermal values. Also, temperature calculations derived from LEED experiments might be in error, due to electron-phonon couplings.     

Recombination of an electron-hole plasma in silicon under the action of femtosecond laser pulses

Experimental data are obtained on the dynamics of conduction-electron relaxation at the stage preceding the melting of a silicon surface layer. The energy of a quantum of probe radiation is smaller than the band gap, making it possible to obtain information about the electron-phonon relaxation processes for an electron concentration of ～ 10²¹ cm^?3 in the conduction band.     

Effect of electron-hole pairs on the melting of silicon

We compute the variation of the melting temperature T_m of silicon, with the density np of electron-hole pairs created by laser illumination: T_m0(1?αnp)2, where α^?11 = 8 × 10²¹ cm^?3. A similar formula is given for amorphous silicon and the application to laser annealing of damaged silicon is discussed.     

Radius of electron-hole drops in silicon

The radius of electron-hole drops at nucleation threshold is investigated as a function of temperature in Si using a small shift of their main luminescence line due to their surface energy. For T > 10 K, experiment and theory are consistent if we take into account a sticking coefficient (～ 4%) at the drop surface. For T ? 10 K our data indicate that the drop size is certainly small, but the measured radii are not likely. This suggests that other effects should be considered, such as the drop curvature energy for example.     

Comment on the electron-hole droplet condensation in direct gap semiconductors

The electron-hole droplet nucleation in highly excited direct gap semiconductors is a non-equilibrium phase transition of second order. Within the framework of a Fokker - Planck approximation modifications of the thermodynamic phase diagram and the cluster distribution function are calculated. Due to the short lifetime of the electronic excitations only very small electron - hole clusters can be formed.