Percolation-based vibrational picture to estimate nonrandom N substitution in GaAsN alloys

Abstract

The number of N atoms in N-rich regions mostly due to nonrandom N incorporation in GaAsN (N∼4%), referred to as the Nr rate, is studied using a nonstandard Raman setup that addresses transverse symmetry. The Ga–N optical range shows a two-mode signal which discriminates between the N-poor (Np) and N-rich (Nr) regions. This is discussed via a percolation-based picture for Be-chalcogenide alloys, which exhibit mechanical contrast with regard to the shear modulus. This applies to GaAs–GaN even though the contrast is in the bulk modulus. The balance of Nr/Np strength provides a Nr rate of ∼30%, i.e., much larger than the corresponding Be rate of ∼4% in random Be-based alloys.

Bi-modal Raman response of Be–Se vibration in Zn1−−Mg Be Se alloys

“…The ZnSe-BeSe percolation picture was recently extended to ZnTe-BeTe [5] and GaAs-GaN [6], with similar mechanical contrast. Possible extension of the above percolation picture to (Be,N)-based multinaries remains unexplored.…”

“…Possible extension of the above percolation picture to (Be,N)-based multinaries remains unexplored. LO Raman spectra recorded with low N-content Ga 1−y In y As 1−x N x epilayers (x ∼ 0.03) [7], show an unassigned mode at ∼425 cm −1 , which corresponds to the location of the (Ga-N) h mode from similar-x GaAs 1−x N x [6], below the well-known (Ga-N) s mode at ∼475 cm −1 . On this basis, the percolation picture might apply to GalnAsN.…”

“…However, very low Be-and Mg-contents can be inferred from strong emergence of the ZnSe-like mode. This makes the detection of the (Be-Se) h mode very unlikely [6], especially by using the less convenient LO symmetry. As a matter of fact a single Be-Se mode was mentioned at ∼450 cm −1 .…”

The atypical temperature evolution of the phonon modes of GaAsN

“…Non-equilibrium growth techniques such as metal organic vapor phase epitaxy (MOVPE) allow the deposition of such metastable layers [5,6]. However, N-clustering and the spontaneous formation of nano-size N-rich regions during layer deposition are energetically preferable over the homogenous distribution of N in the As-sublattice [2,7]. The exact N distribution in these highly mismatched GaAsN alloys depends both on the amount of incorporated N and on the conditions of the layer deposition.…”

“…The phonon modes of GaAsN at room temperature (RT) have been studied intensively by several researchers [7][8][9][10][11][12]. Temperature dependent Raman scattering has been studied for Si [13], GaAs [14], GaN [15], etc.…”