Mechanisms for the reduction of the Schottky barrier heights of high-quality nonalloyed Pt contacts on surface-treated p-GaN

Abstract

X-ray photoelectron spectroscopy (XPS) was employed to investigate the chemical bonding and electronic properties of the interfaces between Pt and p-GaN layers that were two-step surface treated using a buffered-oxide etch solution, and hence, to understand the surface-treatment time dependence of the Schottky barrier height (SBH). Current–voltage (I–V) measurements show that the effective SBH decreases with increasing surface-treatment time. The XPS results show that as the treatment time increases, the Ga 2p and Pt 4f core levels for the 20-min-treated samples shift toward the lower-binding-energy side by 0.6 and 1.5 eV, respectively, compared to the 0.5-min-treated one. It is further shown that the intensity of the oxygen core-level peak decreases with increasing treatment time. Based on the I–V and XPS results, the observed reduction of the effective SBHs is attributed to the combined effects of the effective removal of the native oxide and the shift of the surface Fermi level toward the valence-band edge.

Effects of Surface Treatment on the Electrical Properties of Ohmic Contacts to (In)GaN for High Performance Optical Devices

“…XPS results (not shown) exhibited that the Pt 4f core level peak shifts toward a lower binding energy by 1.5 eV when two-step surface-treated. This indicates that the chemical bonding state of Pt at the interfaces changes from Pt-oxide bonding for the conventional treatment to Pt-GaN bonding for the two-step treatment [9]. This is confirmed by the O 1s core level behaviour, Fig.…”

“…The Ga 2p core level of the surface-treated contact shifts toward a lower binding energy, compared with that of the conventionally treated one. The shift of the surface Fermi level toward the valence band edge was attributed to the increase of carrier concentrations at the surface region of GaN due to the surface treatment [9,10]. Second, it could be related to the effective removal of the native oxide on the GaN surface (and hence the reduction in the SBH).…”

Surface properties of AlxGa1‐xN/GaN heterostructures treated by fluorine plasma: an XPS study

“…Therefore, the XPS experiments reveal the increase in surface potential of Al x Ga 1-x N/GaN heterostructures as a result of the F treatment, and this increase persists even after the fluorinated surface layer is removed. A possible cause for such increase is the removal of donorlike surface states [6], or creation of plasma induced acceptor-like states such as galium vacancy V Ga [16]. These factors could push Fermi level closer to the valence band.…”

“…Due to the lack of surface/interface study, the rise of the effective Schottky barrier height has been solely attributed to the potential modulation by the negatively charged F ions [2]. However, surface treatments, whether through dry or wet means, tend to have strong influence on the surface potential of GaN-based materials [6,7]. In addition, the subsequent Schottky metallization may further modify the interface property and the intrinsic Schottky barrier height (SBH) (ΦΒ, the barrier height at the exact metal/semiconductor interface) [8].…”

High quality tin zinc oxide/Ag ohmic contacts for UV flip‐chip light‐emitting diodes

“…It is noted that Ga 2p 3/2 core level is moved to lower energy side after annealing by 0.32 eV. This indicates that annealing causes a shift of surface Fermi level toward the valence band edge, resulting in reduction in band bending and so Schottky barrier height (SBH) in p type material [4][5][6]. Single 2.5 nm-thick TZO layer was annealed at 530 °C for 1 min in air to investigate the structural morphology of the TZO layer after annealing.…”