THz free-electron laser investigation of GaAsN in pulsed magnetic fields up to 60 T

We use the unique combination of the free-electron laser FELBE and the High Magnetic Field Laboratory Dresden to perform cyclotron resonance (CR) spectroscopy on the dilute nitride alloy GaAsN. FELBE is a tunable (4 – 250 µm) laser source of high brilliance, which can be used in pulsed magnetic fields up to 60 T. Our CR studies enable us to measure fundamental electronic properties of GaAsN, a very interesting candidate for optoelectronic applications because of the tunability of its band gap energy in the range of 1.4 eV – 0.9 eV by the incorporation of a small concentration of N-atoms (~ 1%). Figure 1 illustrates a typical CR spectrum and our values of the CR electron mass at 100 K and 6.5 THz. We observe a slight increase of the electron CR mass with nitrogen content. This dependence is in very good agreement with that described by the band anticrossing (BAC) model [1] and the empirical tight binding (TB) calculations [2], which are represented in Figure 1 by dashed and dotted black lines, respectively. The comparison with magneto-photoluminescence (PL) investigations performed by Alberi et al. [3] and Masia et al. [4] reveal instead a steep increase of the electron effective mass with nitrogen content, which is consistent with a modified k·p calculation by Lindsay and O’Reilly [5]. This model assumes that nitrogen can form pairs and clusters, not considered in [1,2]. Since PL is very sensitive to carrier localization effects, the results in [3,4] can be well described by [5]. In contrast, CR spectroscopy is only sensitive to delocalized states, which explains the good agreement of the present results with [1,2].

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[2] N. Shtinkov et al. Phys. Rev. B 67, 081202(R) (2003).
[3] Alberi et al. Phys. Rev. Lett. 110, 156405 (2013).
[4] Masia et al. Phys. Rev. B 73, 073201, (2006).
[5] A. Lindsay and E. P. O’Reilly Phys. Rev. Lett. 93, 196402 (2004).