Optical spectroscopy in semiconductors in high magnetic fields using polarization modulation

Abstract

Differential magneto-reflection spectra in the 1.8 to 5 eV energy range are presented for GaP, Ge, GaAs, InSb, and Si. These spectra were obtained using polarization-modulated light from [111] faces of samples in the Faraday configuration. In medium strength magnetic fields, the results are similar to those obtained using other techniques, such as electric field modulation and wavelength derivative spectroscopy in the same energy range. In higher magnetic fields ( B of 50 kG or larger) more detailed structure is resolved. Oscillations attributed to Landau level transitions have been seen at critical points in the visible in InSb and in GaSb in fields up to 100 kG. At the E 1 edge an unexpected anomaly has been observed in InSb. Within experimental error, the Landau levels are equally spaced for n < 5 and n > 5 but at n = 5 there is an abrupt change in the cyclotron energy. Here n is the usual magnetic quantum number. The transverse masses are measured as m μ 1 = 18.9 ± 0.9 (n < 5) , and m μ 2 = 16.0 ± 0.9 (n > 5) . Possible causes of this effect are discussed. In GaSb at the corresponding threshold. Landau level observations give a mass value of m μt = 21.4 ± 1.5 .