Characterization Of Gallium Nitride Research Articles

Gallium nitride thin films by microwave plasma-assisted ALD

Synthesis and characterization of gallium nitride (GaN) thin films via microwave plasma-assisted atomic layer deposition (MPALD) is reported in this research. The GaN thin films grown by this technique were amorphous or nanocrystalline as it was demonstrated by electron microscopy. The optical response of these GaN thin films showed a broad peak between 400 nm and 750 nm wavelengths due mostly to carbon and oxygen impurities as has been demonstrated by XPS. That emission from these GaN thin films is located at the border of white and yellow-green emission according to CIE 1931 chromaticity diagram with coordinates, x = 0.3491 and y = 0.4312.

Structural and Optical Properties of GaN Thin Films Grown on Si (111) by Pulsed Laser Deposition

In this work we present results and analysis concerning the processing and characterization of Gallium Nitride (GaN) thin films (TF) grown on Si (111) substrates by pulsed laser deposition technique (PLD), which were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and Raman spectroscopy (RS). The GaN films showed the hexagonal phase with a preferential orientation in the (100) direction, SEM pictures showed a cauliflower-like morphology. Room temperature PL studies showed the so called GaN-yellow band, at 2.29 eV, as well as the donor-acceptor (DA) pair luminescent transition around 3.0 eV. At 10 K, phonon replicas, separated by 69 meV, were observed. By RS, the optical mode on 710 cm-1 was observed, corresponding to the longitudinal optical phonon, A1(LO), as reported for this material.

Design and characterization of GaN p-i-n diodes for betavoltaic devices

The performance of gallium nitride (GaN) p-i-n diodes were investigated for use as a betavoltaic device. Dark IV measurements showed a turn on-voltage of approximately 3.2V, specific-on-resistance of 15.1mΩcm2 and a reverse leakage current of −0.14mA/cm2 at −10V. A clear photo-response was observed when IV curves were measured under a light source at a wavelength of 310nm (4.0eV). In addition, GaN p-i-n diodes were tested under an electron-beam in order to simulate common beta radiation sources ranging from that of 3H (5.6keV average) to 63Ni (17keV average). From this data, we estimated output powers of 53nW and 750nW with overall efficiencies of 0.96% and 4.4% for our device at incident electron energies of 5.6keV and 17keV corresponding to 3H and 63Ni beta sources respectively.

Synthesis of two-dimensional gallium nitride via spin coating method: influences of nitridation temperatures

This paper reports the synthesis and characterization of gallium nitride (GaN) thin films deposited on p-type silicon (100) substrates by using low cost spin coating method under various nitridation temperatures. This work demonstrated that spin coating with the new prepared precursor solution can be used as a versatile method for the successfully growth of GaN thin films. Furthermore, the influence of varying nitridation temperatures on the structural, morphological, and optical properties of synthesized GaN thin films were studied in this work. The GaN thin films were characterized by X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, photoluminescence and Raman spectroscopy. All the characteristics of the GaN thin films were effectively improved with the increasing of the nitridation temperatures from 750 to 950 °C and degraded at temperature of 1,050 °C. The measured results show that nitridation temperature plays an important role in improving the crystalline quality of the GaN thin films and the most efficient nitridation temperature was at 950 °C.

Gallium nitride nanowire nonvolatile memory device

We report the fabrication and characterization of gallium nitride (GaN) nanowire nonvolatile memory field-effect transistors (FETs). The memory device was implemented using a top-gate GaN nanowire FET with an oxide layer as a storage node. A 40nm thick silicon dioxide layer was embedded between the top metal gate and the nanowires, which was deposited using plasma enhanced chemical vapor deposition. Charges were stored in and released from the oxide layer by applying negative and positive gate biases, respectively. It is suggested that charge transport at the gate edge is responsible for the write and erase mechanisms. The locally enhanced electric field at the gate edge induces Fowler-Nordheim tunneling from the metal gate, while the much lower field near the interface between the oxide and the nanowire channel suppresses charge transport.

Improved quality GaN films grown by molecular beam epitaxy on sapphire

We report on the epitaxial growth and characterization of gallium nitride by molecular beam epitaxy (MBE). The samples were grown on (0002) sapphire using solid metal group III sources and an EPI UniBulb™ rf plasma source to produce atomic neutral nitrogen species. The films were characterized optically using reflectance and photoluminescence, van der Pauw Hall effect measurements, and x-ray rocking curves for the (0002), (101̄4), and (22̄04) directions. Nominally undoped films were grown with a (0002) rocking curve (ω) full width at half maximum (FWHM) from 700 to 125 arcsec, electron mobilities of up to 180 cm2/V s, and background carrier concentrations from the mid- 1017–2×1016/cm3. The room temperature photoluminescence FWHM for these films ranged from 38 up to 62 meV, with peak to yellow ratios from 7 to 70. These values represent an improvement in the quality of nominally undoped heteroepitaxially grown GaN by MBE.

Crystal Growth and Characterization of Gallium Nitride

The crystal growth of gallium nitride has been investigated by using the ammonolysis of gallium suboxide, the sublimation of gallium nitride or gallium oxide in an ammonia atmosphere, and the ammonolysis of gallium monochloride at 1150° ± 20°C in gas flow systems. The first two techniques have produced only low resistivity gallium nitride crystals of millimeter size. The ammonolysis of gallium monochloride is most promising; single crystals of gallium nitride as large as 25 × 15 × 5 mm, heretofore unknown, have been obtained by using sapphire platelets with main faces of (102) orientation as substrates. The single crystallinity of these crystals was verified by chemical etching and optical microscopy and x‐ray diffraction techniques. These crystals, with an electron concentration of about 1010 cm−3 and Hall mobilities of about 150 cm2 V−1 sec−1 at room temperature, have been used as substrates for the growth of large gallium nitride crystals of improved structural perfection.