Multiphonon resonant Raman scattering in high-manganese-concentrationCd1−xMn

Abstract

We have measured resonant Raman scattering and photoluminescence (PL) from Cdl Mn"Te (111) films deposited on (111)-oriented GaAs substrates. Film thickness varied from 0.6 to 1.8 pm and manganese concentrations x varied from 0.44 to 0.70 in the seven samples produced for this study using pulsed laser evaporation and epitaxy. Raman scattering shows that the films are of high quality throughout the composition range. The "CdTe-like" and "MnTe-like" LO-phonon modes appear in combinations up to the eighth order at 13 K under outgoing resonance conditions near the Eo gap PL emission peak. Using Raman LO-phonon energy-composition relations reported in the literature for bulk Cd, , Mn"Te, we have estimated the film Mn compositions and found them to be in close agreement with values obtained using energy-dispersive x-ray analysis (EDAX). The PL peak energy was also used to estimate the manganese composition. The best agreement with the Raman and EDAX determinations results when the PL emission is interpreted as being due to a neutral acceptor-bound magnetic polaron instead of an exciton process.The bulk Cd, , Mn"Te (CMT) semiconductor alloy system has been studied extensively because of the wide tunability of its gap (1.58 to 2.30 eV as x ranges from 0 to 0.7) and the many novel properties and potential applica-

Pulsed Laser Evaporation and Epitaxy

“…In particular, LO-phonon overtones higher than order n = 4 have been observed for samples with high-range-Mn-concentration. Figure 12 shows the Raman spectum for a PLEE Cd0.44Mn0.56Te sample [5]. The phonon replicas occur at multiples and combination of the "CdTe-like" LO 1 and "MnTe-like" LO2 phonon frequencies up to eighth order.…”

“…These results indicate that, in terms of crystallographic stucture and chemical purity, the film corresponds to the best bulk material attainable. The resonant Raman scattering and PL experiments which were carried out [5,28,29] for films with 0 < x ≤ 0.70 demonstrate that the films are of high quality throughout the composition range. In particular, LO-phonon overtones higher than order n = 4 have been observed for samples with high-range-Mn-concentration.…”

“…It has been claimed that the quality of laser-grown stuctures can be (221) comparable or even better than that of stuctures grown today with state-of-the-art techniques such as MBE or metal-organic chemical vapour deposition (MOCVD). The first observation of the quantum Hall effect in HgTe-HgCdTe superlattices has been recorded in a laser-MBE grown system [3]; the first observations of high order (n = 8) outgoing resonance Raman spectra for Cd1-xMnxTe have been recorded for PLEE grown material [5] and quantum confinement has been observed in PLEE CdTe-Cd0,90Mn0,10Te quantum well structures [6].…”