Optical Properties Of InN Research Articles

Improved theoretical model of InN optical properties

AbstractThe optical properties of InN are investigated theoretically by employing the projector augmented wave (PAW) method within Green's function and the screened Coulomb interaction approximation (GWo). The calculated results are compared to previously reported calculations which use local density approximation combined with the scissors‐operator approximation. The results of the present calculation are compared with reported values of the InN bandgap and with low temperature near infrared luminescence measurements of InN films deposited by a modified Ion Beam Assisted Deposition technique. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of carbon on the electrical and optical properties of InN, GaN, and AlN

Carbon is a common impurity in the group-III nitrides, often unintentionally incorporated during growth. Nevertheless, the properties of carbon impurities in the nitrides are still not fully understood. We investigate the impact of carbon impurities on the electrical and optical properties of GaN, AlN, and InN using density functional calculations based on a hybrid functional. We examine the stability of substitutional and interstitial configurations as a function of the Fermi-level position and chemical potentials. In all nitrides studied here, C${}_{\mathrm{N}}$ acts as a deep acceptor and gives rise to deep, broad photoluminescence bands. Carbon on the cation site acts as a shallow donor in InN and GaN, but behaves as a $DX$ center in AlN. A split interstitial is the most stable configuration for the C impurity in InN, where it acts as a double donor and likely contributes to $n$-type conductivity.

Electronic Structure and Optical Properties of InN: A First-Principles Study

The electronic properties and the optical properties of wurtzite InN are studied by the first-principles calculations based on the density functional theory. The calculations are based on the Generalized-Gradient Approximation (GGA) and implemented in Plane Wave Self-Consist Field (PWSCF). The optical properties of InN are investigated by the pseudo-potential method with PBEsol-GGA within the WIEN2K program. Band structure, density of states and dielectric functions are calculated detailedly. The energy transitions are observed and compared existing data at critical points. Moreover the new peak in between the region 12 eV to 14 eV should be due to transitions from the In-5p states to the N-2s states.

Effect of Ni Charge States on Structural, Electronic, Magnetic, and Optical Properties of InN

The first-principles study of Ni-doped InN has been carried out to explore the doping effect of various charge states of Ni on the structural, electronic, magnetic, and optical properties of InN using generalized gradient approximation. Structural properties like lattice parameters, aspect ratios, bond lengths, and formation energies of (In, Ni) N are used to determine the stability of each doped system. The formation energies of (In, Ni)N systems decrease with the increase in charge state of nickel, while the bond lengths show an opposite trend. The DOS diagram shows that the introduction of Ni-d states within the bang gap region reduces the band gap for Ni(1+)- and Ni(2+)-doped InN, while the isolated states are generated in the case of Ni(3+)- and Ni(4+)-doped systems. The Ni(1+)-, Ni(3+)-, and Ni(4+)-doped InN systems are ferromagnetic in nature, whereas the (In, Ni(2+))N depicts spin-glass-like behavior. The best possible magnetization is obtained for (In, Ni(4+))N with a total magnet moment of 2.42 μB per supercell. Because of the presence of nickel impurities, the optical properties of InN have been significantly improved. The pure and Ni(3+)- and Ni(4+)-doped InN systems show nearly the same values of absorption edges (∼0.56 eV), in contrast with the Ni(1+)- and Ni(2+)-doped systems, where these values are 0.37 and 0.51 eV, respectively. The shift in absorption edges of Ni(1+)- and Ni(2+)-doped InN to lower energies and increase in the intensity of absorption and broadening of absorption peaks can be attributed to the pronounced band-gap reduction for these systems. A negligible shift of absorption edges in the case of Ni(3+)- and Ni(4+)- doped InN is the characteristic of isolated charge states introduced around the Fermi level, which inhibit the band gap reduction, and hence the optical properties are not improved as expected. This study demonstrates an important fact that for best possible optical device applications Ni(1+)-doped InN system is excellent, while for better magnetic properties the (In, Ni(4+))N is more suitable.

Ab-initio study of electronic and optical properties of InN in wurtzite and cubic phases

We have performed systematic first principle calculations for the electronic and optical properties of a narrow band gap semiconductor InN in cubic and wurtzite phases by ‘state-of-the-art’ DFT calculations within generalized gradient approximation (GGA) and Engel–Vosko's corrected generalized gradient approximation (EVGGA) using full potential linear augmented plane wave (FPLAPW) method as implemented in WIEN2k code. The total energy for the wurtzite phase of InN was found to be smaller by 0.0184 Ry/molecule by cubic phase which confirms the greater stability of the wurtzite structure than the cubic one. Band structure, effective masses, density of states, valence charge densities, and dielectric functions are computed and presented in detail. The critical points are extracted out of calculated dielectric function, compared with available measured data and are explained in terms of transitions occurred in the band structure along different symmetry and antisymmetry lines. The valence band maxima and conduction band minima are strongly dominated by N-2p states and located at the Γ-symmetrical line which predicts its direct band gap nature in both phases.

Structure and optical properties of InN and InAlN films grown by rf magnetron sputtering

The structure and optical properties of InN and In-rich InAlN films grown by magnetron sputtering were investigated. The XRD results show that these films are highly c-axis oriented. The film morphology and microstructure of these films were observed by AFM and SEM which reveals that the films grown in island growth mode. Optical properties of these films were studied by absorption method. The band gap energy of the InN film grown under substrate temperature of 400 °C is 1.38 eV. By studying the E g values of InN films deposited under different substrate temperature, the Burstein-Moss effect on band gap of InN was examined. The significant band gap bowing of our In-rich InAlN films was found to be correlated with the In contents. The bowing parameter of 3.68 eV was obtained which is in agreement with previous theoretical predictions.

Electrical and optical properties of InN with periodic metallic in insertions

We report on a growth by molecular beam epitaxy of InN:In semiconductor/metal composite structures containing periodically inserted arrays of In clusters formed by intentional deposition of In metal films in a thickness range of 2–48 monolayers. It was found that indium insertions do not change markedly carrier mobility in the composites, that remains in the 1300–1600 cm2/(V s) range, while carrier concentration increases with rising In amount. Spectra of thermally detected optical absorption do not exhibit a noticeable Burstein-Moss shift of a principal absorption edge with increasing the carrier concentration, but rather complicated modification of their shapes.

A comparative study of electrical and optical properties of InN and In0.48Ga0.52N

We present results of our studies concerning electrical and optical properties of In0.48Ga0.52N and InN. Hall measurement were carried out at temperatures between T=77 and 300K. Photoluminescence (PL) spectrum in InN and In0.48Ga0.52N. InN has a single peak at 0.77eV at 300K. However, the PL in In0.48Ga0.52N has two peaks; a prominent peak at 1.16eV and a smaller peak at 1.55eV. These two peaks are attributed to Indium segregation corresponding to a high Indium concentration of 48% and a low concentration of 36%. High electric field measurements indicate that drift velocity that tends to saturate at around Vd=1.0×107cm/s at 77K in InN at an electric field of F=12kV/cm. However, in In0.48Ga0.52N the I–V curve is almost linear up to an electric field of F=45kV/cm, where the drift velocity is Vd=1.39×106cm/s. At applied electric fields above this value a S-type negative differential resistance (NDR) is observed leading to an instability in the current and to the irreversible destruction of the sample.

InGaN Thin Films Grown by ENABLE and MBE Techniques on Silicon Substrates

ABSTRACTThe prospect of developing electronic and optoelectronic devices, including solar cells, that utilize the wide range of energy gaps of InGaN has led to a considerable research interest in the electronic and optical properties of InN and In-rich nitride alloys. Recently, significant progress has been achieved in the growth and doping of InGaN over the entire composition range. In this paper we present structural, optical, and electrical characterization results from InGaN films grown on Si (111) wafers. The films were grown over a large composition range by both molecular beam epitaxy (MBE) and the newly developed “energetic neutral atomic-beam lithography & epitaxy” (ENABLE) techniques. ENABLE utilizes a collimated beam of ∼2 eV nitrogen atoms as the active species which are reacted with thermally evaporated Ga and In metals. The technique provides a larger N atom flux compared to MBE and reduces the need for high substrate temperatures, making isothermal growth over the entire InGaN alloy composition range possible. Electrical characteristics of the junctions between n- and p-type InGaN films and n- and p-type Si substrates were measured and compared with theoretical predictions based on the band edge alignment between those two materials. The predicted existence of a low resistance tunnel junction between p-type Si and n-type InGaN was experimentally confirmed.

Real time optical monitoring of molecular beam epitaxy of InN on SiC substrates

Spectroscopic ellipsometry has been used to monitor in real time and in situ the molecular beam epitaxial growth of InN on SiC substrates. A three-step growth process consisting of (i) low-temperature (200°C) nitridation of the SiC surface, (ii) low-temperature (350°C) nucleation of a thin InN buffer layer, and (iii) growth of the InN epitaxial layer at 450°C has been applied. The impact of the In flux on the growth kinetics, morphology, and structural and optical properties of InN has been investigated. It is found that independent of the In flux the low-temperature buffer shows In surface accumulation. This In surface accumulation increases during InN growth under In-rich conditions and is depleted during growth under intermediate and N-rich conditions. Better structural, morphological, and optical properties are obtained when the films are grown under In-rich conditions.

Calculated optical properties of wurtzite InN

We report ab initio, self-consistent calculations of the dielectric function of wurtzite indium nitride (w-InN). Our calculations employed a local density approximation (LDA) potential, a linear combination of atomic orbital basis set, and the Bagayoko-Zhao-Williams (BZW) method. Our findings agree very well with recent measurements up to photon energies of 6eV. This excellent agreement shows the correct description, by the LDA-BZW method, of the relative separations between upper valence bands and low-lying conduction bands, in general, and corroborates our previous result of 0.88eV for the intrinsic, fundamental band gap of w-InN, in particular. We also report results of simulations of the effect of high electron doping on the optical properties of InN.

Superconductivity of InN with a well defined Fermi surface

In this report we present our recent investigation on the co-existence of superconducting and semiconducting properties in InN grown on sapphire (0001) by the use of MBE and MOCVD methods. Magneto-transport measurements were done using InN with a carrier density n e from 4 x 10 17 to 4 x 10 20 cm -3 in the temperature range from 20 mK to 2 K and under the magnetic field (B) up to 23 T. As a result, even InN samples with n e as low as 4 x 10 17 cm -3 showed superconductivity at T c = 0.12 K. The vortex solid of InN was melted by thermal fluctuation and by the external field, similarly to the observation in layered high T c superconductors. By the Shubnikov-de Haas oscillation measurements it was found that there were substantial carriers spread in the a-b plane which played an essential role not only for the occurrence of the superconductivity, but also for many other unexpected electronic and optical properties of InN. Based on these results we present a possible mechanism of superconductivity in terms of the interaction between the conduction electrons and the fixed d-electrons of In atoms spread in the a-b plane.

Electron band structure and optical properties of InN and related alloys

AbstractNew metric system called electron metric system having basic metric constant is introduced. The connection between the electron metric system and the external metric system is defined. The symmetry relationships of the multinary semiconductor compound alloys are defined according to the electron metric system. The basic metric constant is found on the basis of diatomic tetrahedral cell. The electron wave vector in the new system is found and the electron energy states are determined. It is shown correlation between them in the multinary crystal. LCAO electron band structures of Inx Al1–x N and of Inx Ga1–x N are presented. The phenomenon tunnel optical absorption is investigated in Inx Al1–x N, in Inx Ga1–x N, in InN containing oxygen and in non‐stoichiometric InN. It is found the optical absorption edges begin in energies 0.2–1.62 eV that are lower than the energy band gaps due to this phenomenon. Existence of excitons of the structure is shown in these semiconductors and it is found that the peaks of the PL spectra correspond to annihilation energies of these excitons that change in interval 0.5–1.01 eV. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Optical properties of InN with stoichoimetry violation and indium clustering

AbstractWe demonstrate that nonstoichiometry is one of the main reason of strong deviation of the InN optical gap in the 0.7–2 eV range, with N/In < 1 and N/In > 1 corresponding to the lower and higher energies, respectively. The phenomenon is discussed in terms of atomic orbital energies, which are strongly different for indium and nitrogen, therefore both excess atom incorporation and elimination could change the optical gap. We estimate such trends using the approximation of the empirical nearest‐neighbor tight binding theory. It is also demonstrated that resonant absorption in In‐enriched regions is an additional factor lowering an effective absorption edge. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Correlation among growth conditions, crystal structures and optical properties of InN

This paper addresses band-gap issues of InN. InN films of various qualities were prepared by radio-frequency plasma-assisted molecular-beam epitaxy (RF-MBE). Correlation among photoluminescence (PL) peak energy, carrier concentration, electron mobility, PL intensity, PL line width, and X-ray rocking curve (XRC) line width indicated that the InN sample with the smallest PL peak energy of ∼0.67 eV (at room temperature) had the highest electron mobility, the strongest PL intensity even with the smallest electron concentration, the sharpest PL and (0002) XRC peaks. Dependence of PL peak energy on carrier concentration can be explained mostly by the Burstein-Moss shift. Temperature dependence of PL peak energy was normal with smaller values at higher temperatures. These experimental results suggest that the PL should originate from fundamental inter-band transitions and not likely from mid-gap levels associated with crystal defects. These results also suggest that the true band-gap energy of InN should be less than 0.67 eV and probably around 0.65 eV at room temperature. This assessment was further supported by In-composition dependence of PL peak energy for In-rich In1–xGaxN films (also grown by RF-MBE), where room temperature PL peak energy exhibited a monotonic and smooth decrease with the increase in In-composition, approaching to ∼ 0.67 eV of InN. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Modification of InN Properties by Interactions with Hydrogen and Nitrogen

AbstractThe interaction of InN epitaxial films grown by r.f. plasma assisted molecular beam epitaxy with atomic hydrogen and nitrogen, produced by remote r.f. H2 and N2 plasmas, is investigated. InN strongly reacts with both atomic hydrogen and nitrogen yielding depletion of nitrogen and concurrent formation of In clusters. The impact of hydrogen treatments on the optical properties of InN is assessed using photoluminescence (PL). It is found that hydrogen suppresses the intense PL band peaked at approximately 0.7eV for the as-grown InN epitaxial layers, and results in the appearance of a new PL band whose peak energy and intensity increase with H-dose. The effect of exposure to atomic hydrogen and nitrogen on electrical properties of InN is investigated using Hall effect measurements. Atomic force microscopy is also used for studying the morphological changes of InN upon interaction with atomic hydrogen and nitrogen.

Effects of hydrostatic pressure on optical properties of InN and In‐rich group III‐nitride alloys

AbstractWe have used the diamond anvil cell technique to measure the hydrostatic pressure dependence of the optical absorption edge and photoluminescence peak energy of MBE grown InN, In‐rich In1–xGaxN (0 < x < 0.5) and In1–xAlxN (x = 0.25) alloys. Together with previous reports, our results show that the pressure coefficient of the absorption edge varies monotonically from about 3.0 ± 0.1 meV/kbar for InN to 4.2 meV/kbar in GaN and to 4.9 meV/kbar in AlN. The photoluminescence measurements yield significantly smaller pressure coefficients than the coefficients of the bandgap, which is attributed to emission associated with recombination via highly localized defect states. Samples which give small photoluminescence pressure coefficient usually have large Stokes shift. Based on the results of the absorption and photoluminescence measurements we are able to determine the absolute deformation potentials of the conduction and valence band edges of these alloys. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Temperature dependence of the fundamental band gap of InN

The fundamental band gap of InN films grown by molecular beam epitaxy have been measured by transmission and photoluminescence spectroscopy as a function of temperature. The band edge absorption energy and its temperature dependence depend on the doping level. The band gap variation and Varshni parameters of InN are compared with other group III nitrides. The energy of the photoluminescence peak is affected by the emission from localized states and cannot be used to determine the band gap energy. Based on the results obtained on two samples with distinctly different electron concentrations, the effect of degenerate doping on the optical properties of InN is discussed.

Do we know the fundamental energy gap of InN?

We present ab initio calculations of the electronic structure and the optical properties of InN. They are based on a combination of the solutions of the Kohn–Sham equation and quasiparticle corrections. The results are critically discussed in the light of recent experiments. We find an energy gap of InN<1 eV and a non-parabolic absorption edge.

ＩｎＮ薄膜の光学物性

ＩｎＮ薄膜の光学物性