Effects of Mg accumulation on chemical and electronic properties of Mg-doped p-type GaN surface

Abstract

Chemical and electronic properties of Mg-doped p-GaN surfaces were systematically investigated by x-ray photoelectron spectroscopy ͑XPS͒ and Auger electron spectroscopy ͑AES͒. The doping density of Mg ranged from 3ϫ10 19 to 9ϫ10 19 cm Ϫ3 . The XPS and AES analyses revealed the accumulation of Mg for all the air-exposed and chemically treated p-GaN surfaces. The apparent density of Mg calculated from the XPS integrated intensity and the AES intensity was more than one order higher than the value in bulk determined by secondary ion mass spectroscopy. Mg accumulation as well as large amounts of oxides made up the disordered region on the p-GaN:Mg surfaces. Large surface band bending of 1.2-1.6 eV was found at the p-GaN surfaces even after treatment in KOH and NH 4 OH solutions, due to the existence of high-density surface states. It was found that electron cyclotron resonance assisted N 2 -plasma treatment at 300°C for 1 min is very effective in removing such surface disordered regions and reducing surface band bending.

Tuning the surface Fermi level on p-type gallium nitride nanowires for efficient overall water splitting

“…Consequently, the reduction of E F À E V in the nearsurface region, as shown in Fig. 2c, can be directly correlated to the reduction in the downward surface band bending with increasing Mg-dopant incorporation 30,31 . In addition, our detailed analysis reveals that variations in the surface band bending have a very small, or negligible dependence on the morphology of GaN nanowires.…”

Vertical current-flow enhancement via fabrication of GaN nanorod p–n junction diode on graphene

“…Auger emission shoulders seen in Fig. 4(b) are the evidence Ga rich state [24]. emission seen at 3.47 eV originates from a region of pure GaN at the tip of the nanorod, where the optical quality of the hexagonal nanorod is superior to that seen in the base region (exciton bound to a neutral donor, D 0 X).…”

Reduction of Mg segregation in a metalorganic vapor phase epitaxial grown GaN layer by a low-temperature AlN interlayer

“…4 The doping of Mg generally exhibits strong surface segregation. 5 So far, we have obtained an unintentionally high Mg doping level in a nominally undoped top layer. Chang et al reported that the Mg concentration is mostly attributed to the memory effect, i.e., doping mechanism during the metalorganic vapor phase epitaxy ͑MOVPE͒ regrowth due to the residual Mg contamination in the reactor.…”