Detailed analysis of the dielectric function for wurtzite InN and In‐rich InAlN alloys

Abstract

A detailed analysis of the dielectric function (DF) for wurtzite InN as well as for In‐rich InAlN alloys is presented. The experimental data, covering the energy range from 0.72 up to 9.5 eV, were obtained by ellipsometric studies of an (11&2macr;0) a‐plane InN film and low carrier density (0001) c‐plane films. Model calculations of the imaginary part of the DF around the band gap provide direct insight how to determine the energetic position of the Fermi energy from the experimental results. Then, taking into account both, band gap renormalization and Burstein–Moss shift, the values of the gaps at zero carrier density are calculated. The dependence of the InAlN band gap on the alloy composition is described by a bowing parameter of 4.0 eV. The a‐plane film exhibits a characteristic optical anisotropy below 1 eV which is attributed to the polarization dependence of transition probabilities from the three valence bands at the Γ point of the Brillouin zone into the conduction band. The splitting of 25 meV between the absorption edges for the two polarization directions can be well explained by a crystal field energy of 19 (24) meV if a calculated spin–orbit energy of 13 (5) meV is assumed. All results emphasize a band gap value of wurtzite InN of about 0.68 eV. By fitting the third derivatives of the dielectric function up to 9.5 eV we determine the compositional dependences of the transition energies for at least three critical points of the band structure. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

PAMBE growth and in‐situ characterisation of clean (2 × 2) and (√3 × √3) R30° reconstructed InN(0001) thin films

“…The unique physical properties of the semiconductor indium nitride (InN) have a perspective for implementing this compound in optoelectronic, transistor and sensor applications as well as in solar cells [1,2] due to its small band gap [3,4], highest achievable drift velocity of all known semiconductor materials [5,6] as well as its extremely high electron mobility. Particularly, the possibility of producing high efficiency InN-based terahertz emitters facilitates a wide variety of applications [7,8].…”

Widely power-tunable polarization-independent ultrafast mode-locked fiber laser using bulk InN as saturable absorber

“…In the above-described laser, the InN saturable absorber is placed so that its <0001> crystallographic axis is aligned with the laser cavity. In such a configuration, the optical asymmetry within the basal plane of InN is too small [37] to induce remarkable changes with polarization of the incident light. Thus, the mode-locked threshold is independent of the laser polarization.…”

AlInN/GaN based multi quantum well structures – growth and optical properties

“…Still Al 1-x In x N is the less explored nitride alloy since its growth is challenging which is related to the different binding energies of the binaries AlN and InN [7]. Among the topics that are still discussed are the deviation from Vegards rule [8,9] and the band gap bowing [2,10] of the alloy. In this paper the structural and optical properties of Al 1-x In x N / GaN multi quantum wells (MQW) with 0.27 < x < 0.34 will be discussed.…”

“…It spans the whole range of band gap energies from InN (0.68 eV) [1] to AlN (6.2 eV) [2], it can be grown lattice matched (LM) to GaN and even then has a high refractive index contrast [3]. Due to the high polarization induced sheet charge densities, it is of great interest for high performance and high frequency electronic devices [4,5].…”

“…3.2 Band structure Knowledge of the band structure is essential for a better understanding of the luminescence properties of the AlInN/GaN MQW structures. The bowing parameter of the bandgap is still under discussion [2,10] and the valence band offset (VBO) in heterostructures is even less explored. XPS measurements have been performed to study the VBO of AlInN / GaN heterostructures.…”