Remote plasma-enhanced atomic layer deposition of gallium oxide thin films with NH₃ plasma pretreatment

Abstract

High quality gallium oxide (Ga2O3) thin films are deposited by remote plasma-enhanced atomic layer deposition (RPEALD) with trimethylgallium (TMG) and oxygen plasma as precursors. By introducing in-situ NH3 plasma pretreatment on the substrates, the deposition rate of Ga2O3 films on Si and GaN are remarkably enhanced, reached to 0.53 and 0.46 Å/cycle at 250 °C, respectively. The increasing of deposition rate is attributed to more hydroxyls (–OH) generated on the substrate surfaces after NH3 pretreatment, which has no effect on the stoichiometry and surface morphology of the oxide films, but only modifies the surface states of substrates by enhancing reactive site density. Ga2O3 film deposited on GaN wafer is crystallized at 250 °C, with an epitaxial interface between Ga2O3 and GaN clearly observed. This is potentially very important for reducing the interface state density through high quality passivation.

Low Thermal Budget Heteroepitaxial Gallium Oxide Thin Films Enabled by Atomic Layer Deposition

“…In particular, Boschi et al 39 reported ε-Ga 2 O 3 deposited on c-plane sapphire at 550 °C by an unoptimized thermal ALD process (i.e., using water as the oxidant) and indicated that the process conditions need optimization. Hao et al 25 obtained crystalline Ga 2 O 3 films on GaN wafers at 250 °C and observed an epitaxial interface between Ga 2 O 3 and GaN. Roberts et al 32 obtained crystalline gallium oxide films on sapphire at 250 °C which consisted of α-Ga 2 O 3 columns originating from the substrate interface.…”

“…There are only a few literature reports of gallium oxide grown by ALD. − ,− They mostly result in amorphous films that require high-temperature annealing to crystallize. However, there are very few reports ,,,,, of ALD growth of crystalline gallium oxide.…”

“…There are only a few literature reports of gallium oxide grown by ALD. − ,− They mostly result in amorphous films that require high-temperature annealing to crystallize. However, there are very few reports ,,,,, of ALD growth of crystalline gallium oxide. In particular, Boschi et al reported ε-Ga 2 O 3 deposited on c -plane sapphire at 550 °C by an unoptimized thermal ALD process (i.e., using water as the oxidant) and indicated that the process conditions need optimization.…”

Solar‐Blind Ultrathin Sn‐Doped Polycrystalline Ga2O3 UV Phototransistor for Normally Off Operation

“…Ga 2 O 3 can be prepared in five crystallographic stages, namely α, β, γ, δ, and ε, and the β phase is the most used type in electronics applications because of its good chemical and thermodynamic stabilities. [10] Thus far, β-Ga 2 O 3 semiconductors have been prepared using various methods, including molecular beam epitaxy, [11,12] pulsed laser deposition, [13] sputtering, [14] metal-organic chemical vapor deposition, [15] atomic layer deposition, [16] hydride vapor-phase epitaxy, [17] lowpressure chemical vapor deposition, [18] and sol-gel coating. [19] Wafer-scale and high-quality β-Ga 2 O 3 single crystal wafers have also been reported using optical floating zones, [20] Czochralski, [21] and edge-defined film-fed growth [22] methods.…”

“…Thus far, β ‐Ga 2 O 3 semiconductors have been prepared using various methods, including molecular beam epitaxy, [ 11,12 ] pulsed laser deposition, [ 13 ] sputtering, [ 14 ] metal‐organic chemical vapor deposition, [ 15 ] atomic layer deposition, [ 16 ] hydride vapor‐phase epitaxy, [ 17 ] low‐pressure chemical vapor deposition, [ 18 ] and sol–gel coating. [ 19 ] Wafer‐scale and high‐quality β ‐Ga 2 O 3 single crystal wafers have also been reported using optical floating zones, [ 20 ] Czochralski, [ 21 ] and edge‐defined film‐fed growth [ 22 ] methods.…”