Investigation of valence-band splitting in InN by low-temperature photoreflectance spectroscopy

• Published in: Japanese Journal of Applied Physics Vol. 54; no. 3; pp. 31001 - 1-031001-6
• Main Authors: Lin, Kuang-I, Chen, Yen-Jen, Cheng, Yung-Chen, Gwo, Shangjr
• Format: Journal Article
• Language: English
• Published: The Japan Society of Applied Physics 01.03.2015
• Subjects: Band structure of solids; Diffraction; Electronics; Free electrons; Molecular beam epitaxy; Spectra; Spectroscopy; Splitting
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.54.031001

Temperature-dependent photoluminescence (PL) and photoreflectance (PR) spectroscopy and room-temperature Raman spectroscopy and X-ray diffraction have been utilized to investigate the optical properties, electron concentration, crystalline quality, and electronic band structures, especially valence-band splittings, of InN films grown by plasma-assisted molecular beam epitaxy (PAMBE) and metal-organic chemical vapor deposition (MOCVD). The smaller thermal activation energies imply the PAMBE-grown InN film exhibits low-density localized states from band tail states. PR signals of the InN film are detectable when the temperature is below about 100 K due to the cooling down of free electrons to trap states. For the MOCVD-grown InN film, no PR signal is observed even at 15 K due to the higher free electron concentration. To analyze the energetic positions of the features in the PR spectra without ambiguity, the moduli of individual PR resonances are considered. Based on the PR results and appropriate Hamiltonian, the values of the crystal-field splitting and the spin-orbit splitting in InN are experimentally determined as 26.8 and 14.5 meV, respectively. Theoretical and experimental reports are compared and discussed to verify this result.