Donor-acceptor pair recombination and phonon replica in GaSxSe1−x

Solid State Communications

Aytekin

2004

Trap levels in nominally undoped Ga 2 SeS layered crystals have been characterized by thermally stimulated current (TSC) measurements. During the measurements, current was allowed to flow along the c-axis of the crystals in the temperature range of 10-300 K. Two distinct TSC peaks were observed in the spectra, deconvolution of which yielded three peaks. The results are analyzed by curve fitting, peak shape and initial rise methods. They all seem to be in good agreement with each other. The activation energies of three trapping centers in Ga 2 SeS are found to be 72, 100 and 150 meV. The capture cross section of these traps are 6.7!10 K23 , 1.8!10 K23 and 2.8!10 K22 cm 2 with concentrations of 1.3!10 12 , 5.4!10 12 and 4.2!10 12 cm K3 , respectively. q

Section: Initial Rise Methodssupporting

confidence: 55%

Section: Introductionmentioning

confidence: 99%

Trap levels in layered semiconductor Ga2SeS

Aydınlı

Solid State Communications

Aytekin

2004

“…Both peaks show varying degrees of red shift with increasing temperature. The full temperature dependence of the band gap of GaS 0.5 Se 0.5 has been reported in [1][2][3]5], and the temperature coefficient of the band gap was shown to be negative. As the peak energy due to a donor-acceptor pair transition should decrease with the band-gap energy, the observed red shift of the two bands is in agreement with the hypothesis of a recombination over donor-acceptor pairs.…”

Section: Resultsmentioning

confidence: 99%

“…Near band edge luminescence from a series of GaS x Se 1Ϫx mixed crystals have also been measured at T ϭ 4.2 K and attributed to recombination on shallow donor and acceptor states (E A ϭ E D ϭ 25 meV). They were thought to be due to structural defects [2]. However, to our knowledge, there is no data on temperature and excitation intensity dependence of PL spectra in GaS 0.5 Se 0.5 crystals in the literature.…”

Section: Introductionmentioning

confidence: 95%

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Low-temperature photoluminescence study of GaS0.5Se0.5 layered crystals

Aydınlı

Materials Research Bulletin

Goksen

2001

Photoluminescence (PL) spectra of GaS 0.5 Se 0.5 layered single crystals have been studied in the wavelength range of 565-860 nm and in the temperature range of 15-170 K. Two PL bands centered at 585 nm (2.120 eV) and 640 nm (1.938 eV) were observed at T ϭ 15 K. Variations of both bands were studied as a function of excitation laser intensity in the range from 10 Ϫ3 to 15.9 W cm Ϫ2 . These bands are attributed to recombination of charge carriers through donor-acceptor pairs located in the band gap. Radiative transitions from shallow donor levels located at 0.029 and 0.040 eV below the bottom of the conduction band to deep acceptor levels located 0.185 and 0.356 eV above the top of the valence band are suggested to be responsible for the observed A-and B-bands in the PL spectra, respectively. A simple energy level diagram explaining the recombination process is proposed.

Anharmonic Line Shift and Linewidth of the Raman Modes in GaS0.75Se0.25 Layered Crystals

Pala

2002

phys. stat. sol. (b)

PACS: 63.20.Ry; 78.30. Hv The frequencies and linewidths of five Raman-active modes in a GaS 0.75 Se 0.25 layered crystal have been measured in the 10-300 K temperature range and in the 10-380 cm --1 frequency region. We observed softening and broadening of the optical phonon lines with increasing temperature. The analysis of the experimental data showed that the temperature dependencies of frequencies and linewidths are well described by considering the contributions from thermal expansion and lattice anharmonicity. The purely anharmonic contribution (phonon-phonon coupling) is found to be due to three-phonon processes.