Improved Ohmic contacts to plasma etched n-Al0.5Ga0.5N by annealing under nitrogen ambient before metal deposition

Abstract

The contact characteristics of Ti/Al and Ti/Al/Ni/Au contacts to as-grown, plasma etched and plasma etched + annealed in N2 n-Al0.5Ga0.5N epilayers were compared. After a rapid thermal annealing, both Ti/Al and Ti/Al/Ni/Au contacts to as-grown and plasma etched + annealed in N2 n-Al0.5Ga0.5N became truly Ohmic, whereas the contacts to plasma etched samples still remained rectifying. Surface atomic concentration analysis indicates the N vacancies resulting from plasma treatment act more as deep-level states rather than shallow donors. However, these deep-level states could be effectively removed by annealing the plasma etched n-Al0.5Ga0.5N under N2 ambient, and as a result, the Fermi level was elevated toward conduction band edge, facilitating the formation of Ohmic contacts.

Regulation of surface kinetics: rapid growth of n-AlGaN with high conductivity for deep-ultraviolet light emitters

“…Although the ICP-etching damage is inevitable and unfavorable for the ohmic contact, the high enough electron concentration can counteract the negative effects, and hence simplify the fabrication process of DUV-LEDs by omitting the treatment after etching. 27,28 Moreover in terms of the electron mobility, there is an obvious difference between the two samples, i.e., the mobility of n-AlGaN on 0.2°miscut sapphire (36.1 cm 2 V −1 s −1 ) is about 25% lower than that on 0.5°one (47.9 cm 2 V −1 s −1 ). The low mobility is inferred to originate from the grain boundary scattering of islands as shown in Fig.…”

“…Although the ICP-etching damage is inevitable and unfavorable for the ohmic contact, the high enough electron concentration can counteract the negative effects, and hence simplify the fabrication process of DUV-LEDs by omitting the treatment after etching. 27,28…”

Enhanced Current Transport and Injection in Thin-Film Gallium-Nitride Light-Emitting Diodes by Laser-Based Doping

“…These results are comparable to the trends observed in other reports, which have demonstrated that a lower N/Ga ratio leads to the generation of N vacancies. 28,29 N vacancies located at a shallow energy level E D of approximately 25 meV below the conduction band in GaN are well-known for acting as donors. 30 In the presence of Ga vacancies (V Ga ), the low N/Ga ratio may also be explained by the fact that the generation of N vacancies is more pronounced than that of Ga out-diffusion during the LBSD process.…”

Enhanced the Optical Power of AlGaN-Based Deep Ultraviolet Light-Emitting Diode by Optimizing Mesa Sidewall Angle

“…The epitaxial wafer was etched by using the Cl 2 and BCl 3 mixed gas in the inductively coupled plasma (ICP) system to expose the n-AlGaN layer [17], [18]. The Ti/Al/Ti/Au and Ni/Au/Ni/Au served as the n-and p-electrodes, respectively [19], [20]. The schematic diagram for the cross-section view and the micro-chip fabrication flow of the DUV devices are shown in Fig.…”