Effective Suppression of Amorphous Ga₂O and Related Deep Levels on the GaN Surface by High-Temperature Remote Plasma Pretreatments in GaN-Based Metal–Insulator–Semiconductor Electronic Devices

Abstract

Gallium nitride (GaN) has been considered one of the most promising materials for the next-generation power and radio-frequency electronic devices, as they can operate at higher voltage, higher frequency, and higher temperature, compared with their silicon (Si) counterparts. However, the fresh GaN surface is susceptible to the natural oxidation composed of Ga 2 O 3 , Ga 2 O, and other intermediate oxidation states. Moreover, the oxidized GaN surface no longer features the distinct atomic step-terrace morphology, resulting in a degraded interface when gate or passivation dielectrics are deposited without appropriate pretreatment. It is responsible for the degraded performance of GaN-based devices such as current collapse and threshold voltage instability. In this study, the proposed high-temperature (500 °C) remote plasma pretreatments (RPPs) can play a significant role in addressing the issue of the deteriorated GaN surface exposed to air. Atomic stepterrace morphology was recovered after 500 °C-RPP due to the removal of oxides and suboxides. First-principles calculations verified that Ga 2 O at the GaN surface leads to interface states at ∼2.9 eV (E C −E ∼ 0.4 eV) in the bandgap, which is consistent with the increase of interface states at the E C −E range of 0.4−0.9 eV measured through constant-capacitance deep-level transient spectroscopy. Meanwhile, deep interface states and surface-related current collapse are well suppressed in GaN metal−insulator− semiconductor devices. These improved properties by 500 °C-RPP are generalizable to a broader range, including pre-gate and prepassivation treatment, of which a decent surface/interface is desirable for high-performance GaN-based devices.

Surface Engineering of Metals: Techniques, Characterizations and Applications

“…Plasma treatments have gained significant attention in surface engineering for electronic devices [99]. Plasma etching and deposition techniques allow for the precise control of surface characteristics, such as surface roughness, wettability, and chemical composition.…”

Effective suppression of interface states in recessed-gate MIS-HEMTs by TMAH wet etching

“…In the Ga 2p 3/2 core-level spectra, the binding energies of Ga-O and Ga-N are located at 1117.50 ± 0.05 eV and 1116.25 ± 0.05 eV, respectively. 15,16) The percentage contribution of Ga-O is reduced from 45.5% to 36.6%. This is because TMAH wet etching can effectively reduce the O component on the AlGaN surface.…”