Thermal Annealing Effect Between Ni Film and Mg-Doped GaN Layer

Abstract

The effects of thermal annealing between Ni film and a p-type GaN layer have been investigated. The electrical and optical properties were measured by Hall effect, capacitance–voltage (C–V) and photoluminescence (PL) measurements. The samples activated with Ni film obtained higher effective carrier concentrations than those activated without Ni film. Effective carrier concentrations of 5×1015 and 1×1017 cm-3 were achieved at an activating temperature of 400 °C without and with Ni film. The Ni film may act as a catalyst for the activation of Mg-doped GaN at a temperature less than 500 °C. At a temperature higher than 600 °C, the Ni film may react with the Mg-doped GaN. X-ray diffraction (XRD) analyses indicated that Ni film on Mg-doped GaN transforms to nickel oxide (NiO) and nickel nitride (Ni3N) during thermal annealing in air. The peaks of the PL spectra at 15 K of the samples activated at 600 °C with and without Ni film were observed at approximately 3.2 and 2.9 eV. We suggest that Ni atoms not only enhance hydrogen desorption but also diffuse into the Mg-doped GaN layers to form Ni-compound materials. At a high annealing temperature, impurities such as Ni nitride, nitrogen vacancies or other defects may reduce the carrier mobility and provide an increase in the effective carrier concentrations in the surface region.

Glass-Based Transparent Conductive Electrode: Its Application to Visible-to-Ultraviolet Light-Emitting Diodes

“…Figure c shows the XRD spectra measured for the p-GaN terminated 385 nm LED before and after the EBD. Before the EBD, only peaks related to GaN and AlGaN was detected; however, after EBD, several peaks related to Ni 3 N and NiO were detected along with GaN- and AlGaN-related peaks . In addition, the peak intensity of GaN and AlGaN was slightly reduced after the EBD.…”

“…The evidence of the in-diffused Ni atoms after the EBD process is clearly shown by the Ni 2p peaks related to the various binding energies of Ni ions, whereas no such Ni 2p peaks were found before the EBD process (Figure S11). Generally, Ni compounds such as Ni 3 N, NiO are known to improve the ohmic behavior of p-GaN by increasing the effective carrier concentration near the surface …”

Highly Efficient Deep-UV Light-Emitting Diodes Using AlN-Based Deep-UV-Transparent Glass Electrodes

“…Only a peak related to the p-AlGaN layer was detected before the PEBD, 39 whereas an additional peak related to the Ni 3 N film was detected along with the p-AlGaN-related peaks after the PEBD. 40 Ni 3 N is wellknown to improve the Ohmic behavior of p-AlGaN by increasing the effective carrier concentration of the p-AlGaN surface. 40 Both the XPS and XRD results are in good agreement with the EELS results, which support the in-diffusion of Ni atoms toward the p-Al 0.4 Ga 0.6 N surface.…”

“…40 Ni 3 N is wellknown to improve the Ohmic behavior of p-AlGaN by increasing the effective carrier concentration of the p-AlGaN surface. 40 Both the XPS and XRD results are in good agreement with the EELS results, which support the in-diffusion of Ni atoms toward the p-Al 0.4 Ga 0.6 N surface. Figure 4b shows the XPS analysis of the Ga 2p core-level spectra for the same sample before and after the PEBD and the annealed 10 nm ITO layer (after removal).…”

“…Similar results were obtained for the XRD spectra measured at the p-Al 0.4 Ga 0.6 N surface (Figure S6). Only a peak related to the p-AlGaN layer was detected before the PEBD, whereas an additional peak related to the Ni 3 N film was detected along with the p-AlGaN-related peaks after the PEBD . Ni 3 N is well-known to improve the Ohmic behavior of p-AlGaN by increasing the effective carrier concentration of the p-AlGaN surface .…”