Indium Nitride Thin Films Research Articles

Hardness, elastic modulus and structure of indium nitride thin films on AlN-nucleated sapphire substrates

The structural properties of epitaxial indium nitride thin films were characterized and related to the mechanical properties as measured by nanoindentation. The seven epitaxial InN films examined were deposited over the temperature range 200–400°C by reactive magnetron sputtering on (0 0.1) sapphire substrates buffered with a thin AlN layer. The hardness, surface texture and crystal quality of the InN films were functions of the deposition temperature, with the maximum hardness (11.2 GPa), the smoothest surface, the minimum c-lattice constant (0.5708 nm), and the minimum (0 0.4) X-ray rocking curve width (0.6°) all occurring at the deposition temperature of 350°C. The crystal quality and the hardness of the InN films degraded at both higher and lower temperatures.

Pulsed laser deposition of epitaxial AlN, GaN, and InN thin films on sapphire(0001)

Epitaxial aluminum nitride (AlN), gallium nitride (GaN), and indium nitride (InN) films were grown by pulsed laser deposition on sapphire(0001) substrates in high vacuum and in a nitrogen ambient of a few mTorr. The films were analyzed using X-ray diffraction, scanning electron microscopy, atomic force microscopy, and room temperature van der Pauw-Hall measurements. The AlN films were single crystalline with AlN(0001)‖sapphire(0001) and AlN[11̄00]‖sapphire[112̄0]. The GaN films were also single crystalline with the same orientation as the AlN films. The InN films were found to have a preferred crystalline orientation with InN(0001)‖sapphire(0001) and InN[11̄00]‖sapphire[101̄0]. The AlN films were insulating. The GaN film grown in high vacuum had an n-type carrier concentration of 1 × 10 18 cm −3 and a mobility of 300 cm 2/V · s. The GaN film grown in 10 mTorr of N 2 had a p-type carrier concentration of 7.5 × 10 18 cm −3 and a mobility of 150 cm 2/V · s. The InN films grown in high vacuum and 5 mTorr of N 2 were both p-type with carrier concentrations of 6.5 × 10 20 and 4.7 × 10 19 cm −3, and mobilities of 30 and 240 cm 2/V · s, respectively.

Structure of indium nitride thin films prepared by RF-magnetron sputtering

Structure of indium nitride thin films prepared by RF-magnetron sputtering

Elemental Composition of Reactively Sputtered Indium Nitride Thin Films

Indium nitride (InN) thin films have been grown on a variety of substrates using low-temperature radio frequency reactive sputtering of indium metal in pure nitrogen plasma. Quantitative compositional analyses of the films, carried out using X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectrometry (RBS), suggest that large amounts of oxygen are present in them. The high concentration of oxygen in our films is attributed to the voided microstructure as revealed by cross-sectional scanning electron microscopy. The XPS studies also suggest that the oxygen incorporated into the films is bonded to nitrogen.

Indium nitride thin films prepared by radio-frequency reactive sputtering

Indium nitride thin films were obtained by the reactive sputtering method. The metallic indium target was sputtered by nitrogen gas with rf magnetron sputtering equipment. The stoichiometric indium nitride film showed high Hall mobility (363 cm2 (V s)−1) and low carrier concentration (5.98×1018 cm−3). To suppress the nitrogen vacancies, the reevaporation of atomic nitrogen from the substrate must be suppressed by lowering the substrate temperature and the resputtering of atomic nitrogen must be minimized by adjusting the total pressure close to the upper limit of the effective pressure for deposition.

Morphology and Low Temperature Electrical Transport in Heteroepitaxial Indium Nitride Films

ABSTRACTThe correlation of low temperature electrical transport with the evolution of heteroepitaxy and morphology for sputtered indium nitride thin films has been studied. A series of indium nitride films were deposited at temperatures ranging from 50 -650 °C by reactive rf magnetron sputtering onto the (00.1) face of sapphire. Above 350 °C, a transition occurs from a continuous morphology, in which grains are in intimate electrical contact, to an open, porous morphology with poor electrical contact. This transition in morphology deeply affects the electrical transport of the semiconductor. At low deposition temperature, the electrical transport is dominated by the relatively weak intergrain scattering leading to films with moderate mobility. As the deposition temperature is raised, the increasingly porous nature of the film leads to a deterioration in electrical mobility. It is proposed here that the relevant physics of these films is analogous to that for granular solids with a distribution of electrical connectivities that suggests a scattering potential dominated by disorder. In fact, the temperature dependence of the resistivity is found to be analogous to that observed in disordered and amorphous materials. In particular, the resistivity is characterized by: 1) A very weak temperature dependence; 2) The observation of a resistance minimum; and, 3) A steep rise in the low temperature (<4K) resistivity that follows a T1/ dependence.

Overgrowth of indium nitride thin films on aluminum nitride nucleated (00.1) sapphire by reactive magnetron sputtering

The growth and properties of thin films of InN on (00.1) sapphire and (00.1) sapphire nucleated by a 400 Å layer of AlN have been found to be radically different. The unnucleated InN films exhibit a mixed morphology (largely textured with lesser amounts of epitaxial grains), a monofunctional thickness dependence on sputtering time, uniformly low mobility and carrier concentration, and high resistivity. In contrast, the AlN-nucleated overlayers show only heteroepitaxial grains, a bifunctional dependence for the film thickness and surface roughness on sputtering time, higher mobility and carrier concentration, and lower resistivity−even in the limit of an InN overlayer on the order of 20–40 Å.

Optical properties and microstructure of reactively sputtered indium nitride thin films

The optical properties of reactively sputtered InN thin films were measured in the spectral region 2.5–5.5 eV using spectroscopic ellipsometry. The measured pseudodielectric function data of the InN films were found to vary with deposition power. The effective medium approximation theory, which describes a random aggregate microstructure, was able to relate the differences in the measured optical properties to the surface microroughness and porosity of the InN films. The relationship between microstructure and deposition power was subsequently verified by scanning electron microscopy. The analysis and electron microscopy indicate that the film deposited at 90 W was most representative of InN.

Optical band gap of indium nitride

Room-temperature optical absorption data in the 1.5–2.5-eV range are reported for indium nitride thin films prepared by reactive radio-frequency sputtering. The fundamental absorption edge in high-purity material is located at 1.89±0.01 eV and corresponds to a direct transition at k=0, in agreement with band-structure calculations. A significant Moss-Burstein shift is noted for carrier concentrations in excess of 1019 cm−3 and obeys the empirical relationship EG =1.89+2.1×10−8 n1/3 eV.