Hyper-Raman Scattering on GaN and CdS

Abstract

Introduction. In the recent years hyper-Raman (HR) scattering has become an important tool besides Raman scattering to obtain information about structural phase transitions or infrared and Raman-inactive (so-called silent) vibrational modes (for a review see, e.g., Ref. [1]). To the best of our knowledge HR measurements on wurtzite crystals were only performed on CdS [2]. We report on results of HR experiments on GaN and compare them with CdS.

Isotopic Heft on the B1l Silent Mode in Ultra-Narrow Gallium Nitride Nanowires

“…However, the B 1 modes are silent (neither Raman nor IR active), and they are observable by a technique termed hyper-Raman scattering (HRS), which is based on a two-photon excitation process. However, as far as we know, they have not been observed by HRS to date . There are a few publications that claim to observe B 1 modes in some wurtzite materials, but there are several discrepancies in the Raman shifts between them.…”

“…However, as far as we know, they have not been observed by HRS to date. 20 There are a few publications that claim to observe B 1 modes in some wurtzite materials, but there are several discrepancies in the Raman shifts between them. Furthermore, the reported spectra show very broad signals around or close to the predicted modes, so they more closely resemble a maximum in the DOS than a phonon at the Γ point.…”

Theoretical treatment of the first-order hyper-Raman scattering in semiconductors

“…The hyper-Raman scattering in GaN 10 and Cu 2 O 11 was reported too. Spectra of the resonant HRS were observed in the CdS and CuBr quantum dots [12][13] .…”

Theoretical treatment of the resonant hyper-Raman effect in a CdS crystal

“…Besides, under resonant conditions the definite excited states are involved in a scattering process and hence the resonant hyper-Raman scattering (RHRS) allows one to obtain an additional information on crystal excitations and their interactions. Experimental investigations of the RHRS of light by optical phonons in SrTiO 3 , ZnSe, TiO 2 , CdS and GaN crystals were reported [4][5][6][7][8][9][10]. Recently the HRS by Γ − 12 phonons in Cu 2 O was observed when the quantum energy of incident radiation was near the two-photon resonance with the 1S yellow exciton [11].…”

“…The RHRS was first observed in a cadmium sulfide crystal [14]. Later the resonant HRS in CdS was reported in some publications [8,10]. Recently the spectra of the RHRS by optical phonons have been recorded and the dependence of the HRS intensity on the wavelength of incident radiation has been measured [15].…”