Some Electrical and Optical Properties of ZnSe

Abstract

Single crystals of ZnSe have been prepared by the vapor growth technique and optical and electrical measurements on these crystals are reported. Analysis of the reststrahlen reflection peak gives 0.026 ev for the transverse optical phonon energy. The longitudinal optical phonon energy is 0.031 ev as calculated from the transverse phonon energy, the static dielectric constant, ε0=8.1±0.3, and the high-frequency dielectric constant, ε∞=5.75±0.1. The effective ionic charge calculated from the Szigetti formula is 0.7±0.1. Exciton absorption peaks associated with the valence and conduction bands in the vicinity of Γ were observed at liquid hydrogen temperature with the principal peak at 2.81±0.01 ev. The exciton reduced mass 0.1 m0 combined with the room temperature electron-to-hole mobility ratio of 12, obtained by preliminary transport measurements on n- and p-type ZnSe gives tentative values of 0.1 m0 and 0.6 m0 for the electron and hole masses, respectively. Reflectance was determined by various methods in the range 0.025 to 14.5 ev photon energy and was analyzed by the Kronig-Kramers inversion method to obtain the optical constants in the 1 to 10 ev range. A number of peaks appear in the imaginary part of the dielectric constant. The first set of peaks, 2.7 and 3.15 ev, are believed to be due to exciton and interband transitions at Γ with a spin-orbit valence band splitting of 0.45 ev. The second set of peaks, 4.75 and 5.1 ev, are tentatively assigned to transitions at L with a spin-orbit splitting of 0.35 ev. Other peaks are observed at higher energies.

Electron mobility in ZnSe single crystals

“…An attempt to investigate electron mobility in n-ZnSe crystals was made for the first time by Aven et al [1]. The mobility was measured at several temperatures, however the reliable correlation between the temperature and mobility was not established.…”

Excitons and Photoconductivity in Transition‐Metal Dichalcogenides

“…Since E, < E , for optical phonons in ZnSe [25], and the band width a t low temperatures is small by comparison with MoS,, the shoulder is probably due to ionization of ground-state excitons. This was also the explanation given by Park and McConn; but the scattering model explains why there is no displacement of the peak in photoconductivity.…”

“…The ac values of AG were calculated from equations (12) or (13), and the values of A U or A I correspond to the ordinate value o f 1.0 indicated in each of the figures. A 150 watt tungsten-halogen lamp and Hilger-Watts D330 Grating Monochromator were used as the source of light : the crystals were uniformly illuminated, including the contacts (no photovoltaic effect was observed), and the spectral resolution was 5 25 A. Near the absorption edge in MoS,, the light intensity did not vary fast enough with wavelength to shift the positions of the photoconductivity peaks occurring there.…”

Two‐Photon Absorption by Envelope–Hole Coupled Exciton States in Cubic ZnSe. I. Energy Spectrum of the Hd Term and Valence‐Band Parameters

“…1 Table 6 together with averaged masses mh which are gained from non-band selective measurements [20,211. The reasonable agreement between mh and i?ih confirms the experimental data given in Table 5.…”