Domain Matching Epitaxy of Mg-Containing Ag Contact on p-Type GaN

Abstract

We present the epitaxial growth of Mg-containing Ag film on p-type GaN using domain matching epitaxy. No epitaxial growth was found in the asdeposited Ag film, but it changed to epitaxial growth as Mg atoms were added into Ag film. This is due to the fact that Mg atoms were preferentially bonded to O ones, which played a role in shrinking the surrounded Ag lattice from 4.0871 to 4.0858. In addition to that, the volume expansion induced by MgÀO chemical bonding moves the Ag atoms to the site where they are energetically most stable at the Ag/GaN interface, resulting in strong adhesion between Ag films and GaN substrate. As a result, nine domains of the (111)-oriented Ag layer (2.558 nm) are matched with eight domains of the (0001) GaN layer (2.551 nm). This arrangement has the lowest domain mismatch of 8.9%, resulting in the epitaxial growth of the (111) Ag film with the lowest surface energy. Consequently, the Mg-containing Ag film shows better thermal stability, resulting in the suppression of Ag agglomeration.

Comparison of Chemical, Electronic, and Optical Properties of Mg-Doped AlGaN

“…The result is consistent with the concept that the H passivation of Mg acceptor states decreases with the annealing, thereby activating the p-type doping. Using a logarithmic resistance plot, we have determined the activation energy of Mg acceptor states to be 0.2–0.3 eV after the postgrowth annealing, which is consistent with previous findings. − The acceptor activation energy of 0.6 eV, estimated for the as-grown film, also agrees with previous results…”

“…The Mg-doped Al ( x ) Ga (1– x ) N semiconductor crystals have attracted great scientific and technological interest. − Undoubtedly, the most important application of the p-type Mg-doped Al ( x ) Ga (1– x ) N crystals has been the blue LEDs which have enabled the energy-efficient lighting. − Furthermore, various applications of Mg-doped Al ( x ) Ga (1– x ) N are under intensive research and development: for example, high electron-mobility transistors, − ultraviolet LEDs, ,,, gas sensors, − and electrodes of the photoelectrochemical cells. ,, …”

Ohmic Contacts on p‐GaN

“…The strong Cu oxidation suppressed the reaction between Ag and oxygen, and the formation of Cu oxides at the grain boundaries in the post‐annealed Ag‐Cu contact reduced Ag agglomeration. Song et al applied a Mg‐containing Ag layer onto p‐GaN. The introduction of Mg atoms into the Ag layer caused the Ag atoms to move to sites where they are energetically most stable at the Ag/GaN interface.…”

Hierarchical Ag nanostructures on Sn-doped indium oxide nano-branches: super-hydrophobic surface for surface-enhanced Raman scattering

“…2c and d. 31,32 We measured the contact angle with the different annealing conditions of the substrates as shown in Fig. 3a.…”