Room‐temperature photoluminescence in quasi‐2D TlGaSe₂ and TlInS₂semiconductors

Abstract

We reveal the intrinsic band‐to‐band photoluminescence (PL) in Tl‐based anisotropic semiconductors by means of confocal spectroscopy. The PL achieves largest value for k ⊥ c, where c is the layers stacking axis, and is dependent on polarization. In TlGaSe2, the band edge absorption spectra were determined at different excitation geometry by using techniques of depth‐resolved free‐carrier absorption (FCA) and photoacoustic response (PAR). A strong absorption enhancement is detected in a large spectral area in the near‐surface region lateral to ab plane. The band‐to‐band absorption enhancement is the most probable cause for high PL intensity. The near‐surface behavior, different from the bulk, might implement useful photonic functionality at room temperature (RT). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Band gap exciton in ferroelectric TlInS2: Dimensionality and screening

“…Apart from this, disclosure of the high‐oscillator strength excitons in TlInS 2 at room and higher temperatures is very important not only for better understanding of the interesting optical and other properties of TlMeX 2 semiconductors–ferroelectrics but also for creation of excitonic devices operating at room temperature.…”

Carrier dynamics in highly excited TlInS2: evidence of 2D electron–hole charge separation at parallel layers

“…[3,26] In our previous work, it was discovered that polarization of the emitting light from TlGaSe 2 is outof-layer plane, suggesting the e-h emitting dipoles (excitons) are orthogonal to the crystal layer. [7] Furthermore, we obtained that in TlInS 2 the excitonic PL exhibit a large Stokes shift from the direct exciton absorption. [24] Also, we detected enhancement of the PL intrinsic intensity in TlInS 2 crystals with small additions of B, Ag and Er dopants.…”

“…The SPL emission in TlGaSe 2 , however, is sufficiently lower and the crystal has much higher anisotropy of resistivity in perpendicular and parallel to the layer. [2,7] Another distinctive feature of layered ternary crystals is absence of surface related carrier recombination despite of a long carrier decays. The surface recombination creates profiles of the carrier diffusing toward surfaces pronounced in Si and SiC, [44,49] but those are not observed in TlGaSe 2 and TlInS 2 .…”

“…Thallium based ternary dichalcogenides, akin to TlInS 2 , belong to the class of specific 2D multilayered crystals which obey quite unique properties and attract extensive research interest. [1] The distinct anisotropy in TlInS 2 resistivity, [1,2] optical birefringence, [3,4] magneto-dielectric properties, [5] thermal compressibility [1,6] and band edge absorption [7] in conjunction with crystal phases transitions were reported. Several studies showed that anisotropy effects are the peculiarity of 2D-layered structure.…”

“…The PSFs can make invariant of a to b axis, e.g. this shifting can lead to tilting monolithic structure from [110] to [1][2][3][4][5][6][7][8][9][10]. Even though the PSFs cannot be associated with broken bonds, the PSFs edges may give rise to different stresses and band gap states.…”