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Electrical properties and deep electron and hole traps spectra are compared for undoped n-GaN films grown by hydride vapor phase epitaxy (HVPE) in the regular process (standard HVPE samples) and in HVPE process optimized for decreasing the concentration of residual donor impurities (improved HVPE samples). It is shown that the residual donor density can be reduced by optimization from ∼1017 cm-3 to (2-5)×1014 cm-3. The density of deep hole traps and deep electron traps decreases with decreased donor density, so that the concentration of deep hole traps in the improved samples is reduced to ∼5×1013 cm-3 versus 2.9×1016 cm-3 in the standard samples, with a similar decrease in the electron traps concentration. [ABSTRACT FROM AUTHOR]

We report studies of the morphological, electrical, and optical properties of InN grown by hydride vapor phase epitaxy. The layers have been grown on c-plane sapphire substrates and epitaxial GaN, Al0.7Ga0.3N, and AlN templates grown on sapphire. InN properties are found to depend on template type with improvement of crystal structure in the template substrate order AlN→AlGaN→GaN. X-ray studies reveal InN layers grown on template substrates to be relaxed with lattice constants a=3.542 Å and c=5.716 Å. The Raman spectra and optical gaps of the InN layers, vary with free-carrier concentration in agreement with previous studies. We obtain a value of 2.5±0.2 for the index of refraction of InN. [ABSTRACT FROM AUTHOR]

Blue light-emitting diodes (LEDs) based on InGaN/GaN quantum wells (QWs) with different characters of the system of extended defects (SEDs) threading through the active region have been studied using the current-voltage ( I–U), capacitance-voltage ( C–V), and deep-level transient spectroscopy (DLTS) measurements in the dark and under illumination with white light in a temperature range from 100 to 450 K. The DLTS curves exhibit broad E1 and E2 peaks with amplitudes dependent on the illumination. This behavior can be explained assuming the presence of localized states related to SEDs in the active region of the LED. The LEDs with more developed SEDs are characterized by a greater concentration of donor-type traps, which leads to an increase in the density of free charge carriers in QWs, which screen the electron-hole interaction. This circumstance can be among the factors responsible for a severalfold decrease in the quantum efficiency of such LEDs. [ABSTRACT FROM AUTHOR]

Deep-level transient spectroscopy was used to study the parameters of deep levels in the band gap of epitaxial n-GaN layers after irradiaton of the Schottky barriers with 1-MeV protons to a dose of 10[sup 12] cm[sup -2]. A deep level EP1 with an activation energy of 0.085 eV was introduced by irradiation into the upper half of the GaN band gap. The introduction rate of the corresponding defect was found to depend on the bias voltage applied to the Schottky barrier during irradiation. [ABSTRACT FROM AUTHOR]