Multiple‐Phonon Resonant Raman Scattering in Zn_1–x Cd_xSe Crystals

Abstract

Resonant Raman scattering in bulk Znl-,Cd,Se crystals obtained from the vapour phase by the "free-growing" method is studied experimentally. The existence of seventh-order LO-phonon lines under condition of excitation above the band gap and fourth-order LO-phonon lines under condition of excitation below the band gap is observed for mixed semiconductor crystals for the first time. The obtained ratios of intensities of different lines in multiple-phonon spectra are compared with the results of the theory involving the continuous exciton spectrum as an intermediate state. 3KCIIepHMeHTaJIbHO HCCJleAOBaHO pe30HaHCHOe KOM6HHa4HOHHQe PaCCeRHHe B KpHCTaJI-JIax Znl -,Cd,Se, n0JIyseHHbIX MeTOAOM "CB060AHOrO POCTa". BnepsbIe &JIH CMelllaHHbIX IIOJIyIIpOBOAHHHOB Ha6JIIOAaJIHCb IIpOL(eCCb1 pe30HaHCHOrO KOM6HHa~HOHHOrO PaCCeRHHR BIIJIOTL A0 OHHOBpeMeHHOrO pOX<AeHHR CeMH LO-(POHOHOB IIpH BO36ymAeHHH B 06JIaCTH CO6CTBeHHOrO IIorJIoIueHHH H RO seTbIpeX Lo (POHOHOB IIpH BO36yWAeHHH HHme KpaR CO6CTBeHHOrO IIOI'JIOLUeHHR. npOBeneH0 COnOCTaBJIeHHe IlOJIyseHHJdX 3HaqeHHfi OTHO-

Multi-phonon (percolation) behavior and local clustering of CdxZn1−xSe-cubic mixed crystals (x ≤ 0.3): A Raman–ab initio study

“…The fine structure survives the disappearance of the 2A-band. We conclude that it is intrinsic to Cd x Zn 1−x Se-c and not (entirely) due to the Fano-like interference with the 2A-band as originally proposed by Valakh et al [21][22][23] The main/upper component of the fine structure reinforces at the expense of the minor/lower one when the Cd content decreases. This is consistent with their percolationtype assignment in terms of TO Zn Zn-Se and TO Cd-Se , respectively.…”

“…Zn-Se modes of Cd 0.075 Zn 0.925 Se-c and Cd 0.170 Zn 0.830 Se-c ( Fig. 7) consists of the actual Γ-like TO Cd-Se mode-as we believe along with Kozyrev 29 or is merely due to a Fano-like distortion of the main TO signal as originally advanced by Valakh et al [21][22][23] The latter option cannot be excluded in view of the imperfect Raman selection rules (Sec. IV A).…”

“…modes, respectively. The bimodal pattern behind the main TO feature earlier detected by Valakh et al [21][22][23] was unambiguously evidenced by IR-reflectivity. As apparent in the abundant IR data reported by Kozyrev spanning large-to-dilute Cd contents (x ¼ 0:80 À 0:08, see Fig.…”

“…20 Valakh et al pursued the Raman study using monocrystals (x 0:6) and tackled the TO modes, while generally subscribing to Brafman's view of a basic one-mode behavior for Cd x Zn 1−x Se. 21,22 A problem arose herewith that the TO feature exhibits a clear bimodal pattern at any alloy composition, with a significant contribution outside the main TO-LO band. Through a series of detailed Raman studies, the cited authors developed a view that the presumed unique zone-center TO mode acquired a fine structure due to a Fano interference with a two-phonon acoustic continuum (2A) from the Brillouin zone-edge.…”

Crystal structure and vibrational properties of Cu2ZnSiSe4quaternary semiconductor

“…Furthermore, it is not surprising to also observe under resonant conditions some bands corresponding to multi‐phonon scattering processes , which are registered in the spectra around 470, 580, 670, and 870 cm −1 . The first and the last bands are probably due the overtones of the longitudinal excitations lying in the 235 and 435 cm −1 range, while two other might include their combinations.…”