Effects of (NH4)2Sx treatment on indium nitride surfaces

Abstract

Indium nitride (InN) surfaces treated with ammonium sulfide [(NH4)2Sx] are investigated using Hall effect measurement, x-ray photoelectron spectroscopy (XPS), and scanning Kelvin probe microscopy (SKPM). Upon the (NH4)2Sx treatment, the sheet carrier density is reduced by (0.8–0.9)×1013 cm−2, leading to an increase in the sheet resistance. By numerically solving the Poisson’s equation, the associated upward shift of the surface band bending is derived to be 0.3 eV. XPS characterization shows, on the (NH4)2Sx treated InN surface, the formation of native oxide is effectively suppressed and a covalently bonded sulfur layer with surface In atoms is formed. This surface In–S dipole layer results in an increase in the electron affinity, thus giving rise to a lower surface bending shift (0.2 eV) observed in XPS. The electron affinity increase of 0.1 eV can be deduced, which is consistent with the result obtained by SKPM. Thus, the (NH4)2Sx treatment has been demonstrated to be an effective method for reducing the surface band bending for InN.

Electrical characterization of atomic layer deposited Al2O3/InN interfaces

“…34 Reduced surface bending has also been reported in InN after ammonia sulfide [ðNH 4 Þ 2 S] treatment because of the formation of In-S dipole near the surface. 15,17 Hydrobromic acid (HBr) has been used to remove the native oxide on GaAs surface. 19 As discussed previously, in situ TMA prepulsing has also been used to passivate III-V semiconductors.…”

“…Numerous papers have shown by spectroscopy analysis that acids and bases can effectively remove the native oxide on III-V and III-N semiconductor surface by reacting with the surface atoms. [15][16][17][18][19] After careful chemical treatments, partially unpinning of the InN has also been reported by spectroscopic analysis. [15][16][17][18] The surface defects can also be removed by in situ trimethylaluminum (TMA) prepulsing in an atomic layer deposition (ALD) tool.…”

Stable passivation of InN surface electron accumulation with sulphur treatment

“…InN has the smallest electron effective mass, the largest mobility and highest peak and saturation velocities of the group IIInitrides and therefore, coupled with GaN, it has the potential to produce a variety of novel device applications, including radiation hard, high efficiency multi-junction solar cells [6,7], multi-colour detectors, high-brightness multicolour light emitting and laser diodes [8,9], quantum cryptography [10], and high electron mobility transistors [11]. Previously sulphur passivation has been found to reduce the downward band bending by 0.15 eV and decrease the surface sheet charge density by 30 % [12,13] and thus sulphur passivation can improve InN based device performance. Ideally passivation of InN could result in the surface becoming less chemically reactive and in a reduction of the surface band bending for the lifetime of the devices it is implemented into.…”

MBE growth and characterization of Mn-doped InN

“…Chief among these are the degenerate background electron concentration which characterizes all as-grown films, and the presence of a degenerate surface accumulation layer. 5 Furthermore, there are reports 6,7 of employing sulfur passivation to reduce the surface accumulation layer. 3 Nevertheless, there are experimental techniques to probe beyond the surface accumulation layer to extract the bulk properties, such as electrochemical capacitance-voltage (C-V) profiling, 3 variable magnetic field Hall effect, 4 and thermopower measurements.…”