Ground and Excited States of Excitons in GaSe Single Crystals

Abstract

In this work photoluminescence, reflection and absorption spectra of GaSe single crystals were studied in a wide temperature range (10 – 300 K). The presence of series of excitonic levels in the region E > Eg was shown. At excitation by 448 nm laser of GaSe crystal electrons were resonantly excited from V1(Γ1) band to C1(Γ6) and C2(Γ5) bands. The luminescence from excitonic levels (nA = 1, 2 … 5) of conduction band C1(Γ6) to valence band V1(Γ1) was observed. Recombination from excitonic level of C1(Γ6) band to V2 and V3 bands (maxima nB = 1–2.1751 eV and nB = 2–2.2222 eV) and to V4 and V5 bands (maxima nC = 1 – 2.311 eV and nC = 2–2.350 eV) was observed. Luminescence maxima nD = 1 (2.399 eV) and nD = 2 (2.434 eV) attributed to transitions between C1 – V6, V7 bands and E3 maximum caused by recombination C2 – V1 were found out. A model of energy bands responsible for observed transitions was suggested.