Semiconductor Physics, Quantum Electronics & Optoelectronics. 2002. V. 5, N 2. P. 156-162.

PACS: 71.35.Cc, 78.40.Fy, S8.12

Light absorption by excited exciton states in layered InSe crystals

Yu. I. Zhirko, I.P. Zharkov

Institute of Physics, NAS of Ukraine, 46 prospect Nauky, 03037 Kyiv, Ukraine

Abstract. We investigated spectra of light absorption by excitons in InSe crystals of different thicknesses, both pure and doped with iron group impurities, at temperatures from 4.5 up to 100 К. It was shown that, along with the traditional direct optical transition (photon ® exciton ® photon) at k = 0, exciton production and annihilation (accompanied with photon emission) occurs also via indirect vertical transition (photon ± phonon ® exciton ® photon ± phonon) at k @ 0. For the n = 1 exciton state the direct and indirect vertical transitions were found to be compatible. For excited exciton states these transitions are not compatible; as a result, the integral intensity of absorption bands for excited exciton states, K_n, is over K₀/n₃ (where K₀ is the classic value for the n = 1 exciton absorption band) and grows with temperature. For the n = 1 exciton state both symmetric and asymmetric (with phonon absorption only) indirect vertical transitions are considered.

Keywords: exciton absorption, layered crystal, InSe.

Paper received 26.02.02; revised manuscript received 08.04.02; accepted for publication 25.06.02.

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