This paper is NOT THE PUBLISHED VERSION; but the author's final, peer-reviewed manuscript. The published version may be accessed by following the link in th citation below.

We have studied laser action of ZnSe and ZnS0.05Se0.95 samples grown by seeded physical vapor phase transport (SPVT) technique in the near resonant two-photon absorption regime. The two-photon pumped lasing was observed using a tunable near-infrared nanosecond laser (830–890 nm). Blue lasing could be observed up to 200 K and the two-photon pumped lasing threshold was measured to be ∼7 MW/cm2 at 10 K. This work demonstrates the applicability of using near-infrared diode lasers as pumping sources to excite the ZnSe-based materials. By comparing the energy position of two-photon pumped lasing with that of the one-photon pumped lasing and examining the red shift of the energy position, we suggest that the free-exciton free-exciton scattering and resultant band filling are the dominant processes involved in the lasing action of ZnSe and ZnSSe alloy crystals at low temperature.

Optically pumped lasing of (111) oriented bulk ZnSe grown by seeded physical vapor phase transport (SPVT) technique has been achieved at room temperature under near resonant pumping with the excitation photon energy very close to the fundamental band gap. Laser emission can be seen at a pumping intensity as low as 7 kW/cm2. The lasing mode spacings resulting from the dispersion of the index of refraction for ZnSe in a Fabry–Perot resonator-like cavity have been observed as well. Our experimental results demonstrate that SPVT ZnSe single crystals have the quality sufficient to develop low-threshold, high-power output blue lasers.

Photoluminescence (PL) and thermally stimulated conductivity (TSC) data on high-resistivity, p-type CdTe single crystals are presented. The PL emission in these samples consists of two closely overlapping components peaking at approximately 1.47 and 1.49 eV. Thermal quenching of these signals reveals activation energies of ∼0.02 and ∼0.13 eV for the former component, and ∼0.11 eV for the latter. TSC signals at temperatures corresponding to those over which thermal quenching occurs are observed. The TSC peaks are due to hole release with activation energies which agree with those obtained from the thermal quenching studies. Etching of the samples removes surface damage caused by mechanical polishing. The surface damage produces nonradiative pathways by which electron-hole recombination can take place without luminescence. A model based on free-electron to trapped-hole recombination is presented to account for the data. It is shown, from numerical solutions of the rate equations describing the model, that by explicitly incorporating into the model more than one hole state at which radiative recombination can occur, shifts in the emission energy during time-resolved and intensity-dependence studies can be expected.

We report pressure-dependent photoluminescence (PL) measurements on ZnSe single crystals grown by the seeded physical vapor phase transport technique. Two kinds of ZnSe samples, the as-grown and Zn-extracted single crystals were used in this study. The Id1 line is the predominant spectral feature for the as-grown samples and shifts with pressure at a rate of 7.3 meV/kbar. The I3 emission dominates the PL spectra of the Zn-extracted samples and has a pressure coefficient of 6.6 meV/kbar, which is inconsistent with the assumption of the I3 line originating from the recombination of the excitons bound to ionized donors.

Uniaxial stress dependence of photoluminescence has been employed to study the exciton emission in seeded physical vapor transport ZnSe. By examining the stress behavior of the photoluminescence line Ix , it is suggested that this line is due to recombination of a deep donor-bound exciton. From measurements of the π- and σ-polarized luminescence spectra the heavy-hole and light-hole components of the exciton emissions were followed as a function of applied stress. From these data the linear hydrostatic and shear deformation potential constants were calculated to be a=−5.1 and b=−0.74 eV, respectively.

The optical properties of ZnSe bulk crystals grown by the seeded physical vapour phase transport technique (SPVT) were studied by low-temperature photoluminescence and room-temperature stimulated emission measurements. Large strain-free ZnSe single crystals with a diameter as large as 5 cm have been grown uniformly without twinning by the SPYT technique. A variety of ZnSe samples. the as-grown and post-growth treated as well as intentionally doped crystals, were prepared in this study. Low-temperature photoluminescence measurements showed t h a t near band edge I : line and its LO phonon replicas dominated t h e spectra, a n d that donor-acceptor pair emission signatures w e r e absent for SPVT asgrown samples; the intensity of t h e I : line decreased considerably and the l3 line became predominant after Zn extraction treatment. The pressure dependence on the bound exciton emission lines suggested that t h e l 3 line might originate from excitons bound to a donor-like deep centre rather than to ionized shallow donors. The room-temperature optically pumped stimulated emission and blue lasing f r o m the as-grown samples demonstrated that SPVT ZnSe single crystals have the quality sufficient to develop low-threshold, high-power output blue lasers.

Thermally stimulated conductivity (TSC) data on high-resistivity, p-type CdTe single crystals are presented. The CdTe samples under study were either nominally undoped or doped with Mn or Fe. Deconvolution and peak fitting analysis of the TSC curves consistently revealed the presence of traps at approximately Ev+0.16, Ec−0.24, Ev+0.23, Ev+0.32, Ev+0.39, Ev+0.40, and Ev+0.47 eV in etched samples corresponding to TSC maxima at approximately 95, 110, 120, 145, 165, 170, and 190 K, respectively. An additional TSC peak, believed to be related to surface damage caused by mechanical polishing, is observed at approximately 105 K corresponding to electron traps at Ec−0.21 eV. The evidence indicates that the TSC curve from 80 to 200 K may be best described as a superposition of first-order (slow-retrapping) processes. Frequency factors and capture cross sections are calculated as temperature-dependent power-law functions. Some of the traps have been associated with particular defect structures, however, no clear correlation with the presence of Mn or Fe is observed.