Study of Excitonic Molecules in Monoclinic Zinc Diphosphide Crystals

Abstract

I. S. GORBAN et al. The photoluminescence (PL) spectra of the monoclinic modification of the semiconductor crystal ZnP, (P-ZnP,) are studied under high, intermediate, and low laser excitation intensities at liquid helium temperature. Under high excitation intensities the inverse hydrogenlike M-series was observed. It is symmetrical with the hydrogen-like excitonic series. This M-series is due to the two-electron transitions from the excitonic molecule (biexciton) state to the ground, excited, and ionized excitonic states. The binding energy of the biexciton in O-ZnP, is determined as dbex = 14.9 meV (0.32 of exciton Rydberg). Under intermediate excitation intensities another G-band appears in the PL spectrum of P-ZnP,. This band is interpreted as a result of two-photon annihilation of free excitonic molecules in the gas phase. A narrow C-line appears in the PL spectrum under intermediate excitation intensities, too. The analysis of the temperature dependence of the C-line intensity allows us to assume this line to be the result of two-photon annihilation of the biexcitons condensed into a dielectric liquid with the binding energy A , zz 0.5 meV.

Transient reflectivity changes of β-ZnP2 exciton bands by pump–probe spectroscopy using a femtosecond laser

“…(Note that the ordinate is ÀDR.) In b-ZnP 2 the luminescence from an excitonic molecule, namely a biexciton, appears at 1.550 eV [5,8,9]. Therefore, the structure is reasonably attributed to this biexciton transition.…”

Instabilities and Self-Organization Phenomena in High Density Exciton Systems

“…At high irradiation (in both steady-state and pulse one) authors observed a new narrow line, which was explained as emission from the biexciton liquid state. According to the estimations fulfilled by Gorban et al (1995) authors observed the condensation of the biexcitons due to biexciton-biexciton interaction. It is not Bose-Einstein condensation of particles with wave vectors k ¼ 0.…”

“…But there is an active discussion of these results with another explanation (O'Hara and Wolfe, 2000) due to Auger decay process, spatial distribution of exciton gas. *E-mail: sugakov@kinr.kiev.ua Condensed exciton phase was observed in -ZnP 2 crystals (Gorban et al, 1995(Gorban et al, , 1996. In this crystal there is a strong exciton-exciton interaction that causes the biexciton molecule creation with the inordinately high value of the biexciton binding energy (14.9 meV).…”

“…The phase diagram liquid-gas obtained (Gorban et al, 1996) for biexcitons has the form of a typical phase diagram of first order. Our theoretical consideration has applicability for type of systems which investigated in the articles crystals (Gorban et al, 1995(Gorban et al, , 1996.…”

Excitons and excitonic molecules in mixed Zn(P1−xAsx)2 crystals

“…Emission B-line is due to the radiative transitions from the ground state of forbidden S-orthoexciton and corresponds to B 1 -line of absorption B-series. Serial laws of excitons in ZnP ЕМs manifest themselves in PL spectra due to twoelectron and two-photon radiative transitions from the ground state of a molecule [9][10][11]. Two-electron transitions occur from the ground state of biexciton to states of excitons of C and A-series (further C and Aexcitons correspondingly).…”