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Indium nitride (InN) is characterized by its high electron mobility, making it a ground-breaking material for high frequency electronics. The difficulty of depositing high-quality crystalline InN currently impedes its broad implementation in electronic devices. Herein, we report a new highly volatile In(III) triazenide precursor and demonstrate its ability to deposit high-quality epitaxial hexagonal InN by atomic layer deposition (ALD). The new In(III) precursor, the first example of a homoleptic triazenide used in a vapor deposition process, was easily synthesized and purified by sublimation. Thermogravimetric analysis showed single step volatilization with an onset temperature of 145 °C and negligible residual mass. Strikingly, two temperature intervals with selflimiting growth were observed when depositing InN films. In the high-temperature interval, the precursor underwent a gas-phase thermal decomposition inside the ALD reaction chamber to produce a more reactive In(III) compound while retaining self-limiting growth behavior. Density functional theory calculations revealed a unique two-step decomposition process, which liberates three molecules of each propene and N 2 to give a smaller tricoordinated In(III) species. Stoichiometric InN films with very low levels of impurities were grown epitaxially on 4H-SiC. The InN films deposited at 325 °C had a sheet resistivity of 920 Ω/sq. This new triazenide precursor enables ALD of InN for semiconductor applications and provides a new family of M−N bonded precursors for future deposition processes.

Indium nitride (InN) is an interesting material for future high frequency electronics, due to its high electron mobility. The problematic deposition of InN films currently prevents full exploration of InN based electronics. We present studies of atomic layer deposition (ALD) of InN using In precursors with bidentate ligands forming In-N bonds; tris(N,N-dimethyl-N',N''diisoproprylguanidinato)indium(III), tris(N,N'-diisopropylamidinato)indium(III) and tris(N,N'-diisopropylformamidinato)indium(III). These compounds form a series were the size of the substituent in the endocyclic position decreases from -NMe2, to -Me and to -H, respectively. We show that when the size of the substituent decreases, InN films with higher crystallinity and optical quality, lower roughness and an In/N ratio closer to unity is achieved.From quantum chemical calculations we show that the smaller substituents lead to less steric repulsion and weaker bonds between the ligand and In centre. We propose that these effects render a more favoured surface chemistry for the nitridation step in the ALD cycle which explains the improved film properties.

The first trihydroborate bearing a pentacoordinated phosphorus atom was synthesized as a new P-B bonded compound. Hydride abstraction of the trihydroborate gave an intermediary dihydroborane, which showed hydroboration reactivity and was trapped with pyridine whilst maintaining the P-B bond. The dihydroborane underwent a rearrangement, which involved a double ring expansion to compensate for the unbalanced coordination states of the phosphorus and boron atoms, to give a new fused bicyclic phosphine-boronate.

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