High temperature and low pressure chemical vapor deposition of silicon nitride on AlGaN: Band offsets and passivation studies

Abstract

In this work, we employed X-ray photoelectron spectroscopy to determine the band offsets and interface Fermi level at the heterojunction formed by stoichiometric silicon nitride deposited on AlxGa1-xN (of varying Al composition “x”) via low pressure chemical vapor deposition. Silicon nitride is found to form a type II staggered band alignment with AlGaN for all Al compositions (0 ≤ x ≤ 1) and present an electron barrier into AlGaN even at higher Al compositions, where Eg(AlGaN) > Eg(Si3N4). Further, no band bending is observed in AlGaN for x ≤ 0.6 and a reduced band bending (by ∼1 eV in comparison to that at free surface) is observed for x > 0.6. The Fermi level in silicon nitride is found to be at 3 eV with respect to its valence band, which is likely due to silicon (≡Si0/−1) dangling bonds. The presence of band bending for x > 0.6 is seen as a likely consequence of Fermi level alignment at Si3N4/AlGaN hetero-interface and not due to interface states. Photoelectron spectroscopy results are corroborated by current-voltage-temperature and capacitance-voltage measurements. A shift in the interface Fermi level (before band bending at equilibrium) from the conduction band in Si3N4/n-GaN to the valence band in Si3N4/p-GaN is observed, which strongly indicates a reduction in mid-gap interface states. Hence, stoichiometric silicon nitride is found to be a feasible passivation and dielectric insulation material for AlGaN at any composition.

SiNx/(Al,Ga)N interface barrier in N-polar III-nitride transistor structures studied by modulation spectroscopy

“…Quite unexpectedly a lower surface barrier of ~ 0.35 eV is estimated for the uncapped Al 0.46 Ga 0.54 N terminated structure. In ultra-high vacuum (UHV) conditions a higher initial barrier for GaN and a gradual increase in surface barrier in AlGaN alloys were observed by x-ray photoelectron spectroscopy (XPS) previously 22 . The discrepancy may be related to surface oxidation of samples under study within this work and N-polar nitrides are known to be easily oxidated 30 .…”

“…Examining N-polar GaN/AlGaN structures with an in-situ MOCVD Si 3 N 4 a barrier height of ~ 1 eV at the Si 3 N 4 /GaN interface was determined via capacitance-voltage (C-V) measurements 21 . More recently, the Fermi level at ex-situ Si 3 N 4 /AlGaN interfaces was reported to be located close to the conduction band (CB) over a broad range of Al contents in both metal-and N-polar AlGaN up to 60% 22 .…”

Understanding band alignments in semiconductor heterostructures: Composition dependence and type-I–type-II transition of natural band offsets in nonpolar zinc-blendeAlxGa1−xN/AlyLandmann1, Rauls2, Schmidt3 2017Phys. Rev. B19060View full textAdd to dashboardCite

“…Especially indium containing nitride/arsenide and antimonide/arsenide quantum well or quantum dot heterostructures show promising material characteristics, in this respect [97][98][99][100][101][102][103][104]. Very recently, Reddy et al [105] conducted a x-ray photoelectron-spectroscopy study on the band alignment between silicon nitride (Si 3 N 4 ) and wz-Al x Ga 1−x N. Despite the large (indirect) Si 3 N 4 band gap of 5.3 eV [106], which is comparable to the indirect band gap of cubic zb-AlN, the relative positions of the valence and conduction-edge bands of Si 3 N 4 cause all Si 3 N 4 /Al x Ga 1−x N(0001) interfaces to form a staggered type-II alignment, independent of the nitride-alloy composition. Type-II band alignment for technological application has also been studied in various other semiconducting material classes.…”

Optimization of the CMP Process with Colloidal Silica Performance for Bulk AlN Single Crystal Substrate

“…Group III-Nitride compound semiconductor substrates such as GaN, AlN, and InN are next-generation semiconductor materials that exhibit excellent features such as potential for miniaturization and light weight, low power consumption, and long lifetime of devices; demand for such material is steadily increasing [1,2]. Aluminum nitride (AlN), which has a wide bandgap of 6.2 eV, high thermal stability and thermal conductivity, and wide critical electric fields (12.5 MV/cm), has been applied to AlGaN-based ultraviolet optoelectronic devices; because it can provide superior power properties, it is used mainly as an substrate for various applications ranging from semiconductor devices to laser diodes (LD) and light emitting diodes (LED) [3][4][5].…”