Investigation of oxygen incorporation in AlGaN/GaN heterostructures

Kimura

Phys. Status Solidi (c)

et al. 2006

Electrical properties of Ni/i-AlGaN/GaN heterostructures prepared by various surface preparation conditions have been studied by I-V and C-V measurements. The surface native oxide lowered the effective Schottky barrier height (SBH) accompanied with significant increase of the reverse leakage current. Tunneling together with surface patches seems to take part in the reverse leakage current. Annealing in N 2 improved the effective SBH and the leakage current. The optimum annealing temperature depended on both the surface preparation condition and the Al composition. Insertion of a thin anodic Al 2 O 3 layer between Ni and i-AlGaN effectively reduced the leakage current to 10 -6 A/cm 2 . Hall effect measurements revealed that tharmal annealing of bare i-AlGaN(x = 0.20)/GaN heterostructures, at above 600 °C, leads to reduction of the electron mobility and the 2DEG density.

Section: Resultsmentioning

confidence: 96%

Electrical properties of Ni/i‐AlGaN/GaN structures and influence of thermal annealing

Kimura

Phys. Status Solidi (c)

et al. 2006

Physica Status Solidi (b)

“…In addition, sample D features a lower TDD than sample C. Both effects seem to increase the emission intensity, at least at T = 10 K. 2) The ternary material AlGaN is more susceptible to increased incorporation of point defects, some of which might cause nonradiative recombination. [ 37–40 ] This leads to stronger intensity losses around room temperature when charge carrier localization is overcome. 3) AlGaN layers in the medium range of composition may be subject to a temperature‐dependent change of the occupation of their valence bands which can modify the degree of light polarization and the light outcoupling efficiency when temperature rises.…”

Section: Resultsmentioning

confidence: 99%

Temperature Dependence of Dark Spot Diameters in GaN and AlGaN

Netzel

Knauer

Brunner

et al. 2021

Threading dislocations in c‐plane (Al,Ga)N layers are surrounded by areas with reduced light generation efficiency, called “dark spots.” These areas are observable in luminescence measurements with spatial resolution in the submicrometer range. Dark spots reduce the internal quantum efficiency in single layers and light‐emitting devices. In cathodoluminescence measurements, the diameter of dark spots (full width at half maximum [FWHM]) is observed to be 200–250 nm for GaN. It decreases by 30–60% for AlxGa1−xN with x ≈ 0.5. Furthermore, the dark spot diameter increases with increasing temperature from 83 to 300 K in AlGaN, whereas it decreases in GaN. Emission energy mappings around dark spots become less smooth and show sharper features on submicrometer scales at low temperature for AlGaN and, on the contrary, at high temperature for GaN. It is concluded that charge carrier localization dominates the temperature dependence of dark spot diameters and of the emission energy distribution around threading dislocations in AlGaN, whereas the temperature‐dependent excitation volume in cathodoluminescence and charge carrier diffusion limited by phonon scattering are the dominant effects in GaN. Consequently, with increasing temperature, nonradiative recombination related to threading dislocations extends to wider regions in AlGaN, whereas it becomes spatially limited in GaN.

JSTS:Journal of Semiconductor Technology and Science

“…The electron sheet density increased as the annealing temperature increased further. The increased carrier concentration in the 2DEG is attributed to the incorporation of oxygen donor impurities [12]. The decrease in the electron mobility following annealing is attributed to increased electron-electron scattering.…”

Section: Resultsmentioning

confidence: 99%

“…Various oxygen-annealing methods have been used during the fabrication of GaN devices [12][13][14][15][16][17], and can result in an increased electron concentration of the 2DEG [12], as well as modified Schottky barrier heights and Fermi-level pinning due to the increased density of donor states [13]. Ohmic contacts to p-type GaN require annealing in an O 2 ambient environment at a relatively low temperature [14].…”

Section: Introductionmentioning

confidence: 99%

Contact Resistance and Leakage Current of GaN Devices with Annealed Ti/Al/Mo/Au Ohmic Contacts

Ha¹,

Kang-Min²,

Jo³

et al. 2016

Abstract-In recent years, the on-resistance, power loss and cell density of Si power devices have not exhibited significant improvements, and performance is approaching the material limits. GaN is considered an attractive material for future high-power applications because of the wide band-gap, large breakdown field, high electron mobility, high switching speed and low on-resistance. Here we report on the Ohmic contact resistance and reversebias characteristics of AlGaN/GaN Schottky barrier diodes with and without annealing. Annealing in oxygen at 500℃ resulted in an increase in the breakdown voltage from 641 to 1,172 V for devices with an anode-cathode separation of 20 μm. However, these annealing conditions also resulted in an increase in the contact resistance of 0.183 Ω-mm, which is attributed to oxidation of the metal contacts. Auger electron spectroscopy revealed diffusion of oxygen and Au into the AlGaN and GaN layers following annealing. The improved reverse-bias characteristics following annealing in oxygen are attributed to passivation of dangling bonds and plasma damage due to interactions between oxygen and GaN/AlGaN. Thermal annealing is therefore useful during the fabrication of high-voltage GaN devices, but the effects on the Ohmic contact resistance should be considered.