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Preferential formation of Al-N bonds in low N-content AlGaAsN

Bevorzugte Bildung von Al-N Bindungen in AlGaAsN mit geringem N-Gehalt
: Geppert, T.; Wagner, J.; Köhler, K.; Ganser, P.; Maier, M.


Applied Physics Letters 80 (2002), Nr.12, S.2081-2083
ISSN: 0003-6951
ISSN: 1077-3118
Fraunhofer IAF ()
AlGaAsN; raman spectroscopy; Ramanspektroskopie; Al-N bonding; Al-N Bindung; molecular beam epitaxy; Molekularstrahlepitaxie

The bonding of nitrogen in low N-content Al(x)Ga(1-x)As(1-y)N(y) with x <=0.05 and y <=0.04 has been studied by Raman spectroscopy. Upon the addition of Al to GaAsN, additional vibrational modes are observed at around 450 cm(exp -1), which is below the GaN-like longitudinal optical (LO) phonon mode centered at 470 cm(exp -1). These modes are attributed to the formation of Al and N containing complexes with Al-to-N bonding. With increasing Al content the Al-N related modes gain intensity at the expense of the GaN-like mode, and they become the dominant N-related feature for an Al-content of 5 % at a fixed N content of 1 %. On the other hand, increasing the N content from 0 % up to 4 % at a constant Al concentration of 5 % results first in the appearance and eventual saturation in intensity of the AlN-like modes, accompanied by a steep increase in intensity and eventual dominance of the GaN-like vibrational mode. Simultaneously the AlAs-like LO2 phonon mode shows a drastic decrease in intensity for N contents exceeding 2 %. All these observations strongly indicate that there is a preferential formation of Al-N bonds in low N- and Al-content AlGaAsN, which is in direct contrast to GaInAsN, where even after thermal annealing the GaN-like mode remains dominant in the Raman spectrum compared to the InN-like modes.