Minimizing the low-quality interfacial layer (IL) growth during high-k film deposition on III-V compound substrates has been a major research area, in addition to the development of various interface passivation techniques [1]. On GaAs substrates, Hinkle et al. [2] reported a pioneering work on the metal-organic (MO) precursoractivated self-cleaning effect, a spontaneous clean-up of the surface oxides during the atomic layer deposition (ALD) of HfO 2 and Al 2 O 3 . A similar cleaning effect was also observed on InGaAs [3,4]. Among many contributing parameters, the ALD temperature is known to strongly affect the self-cleaning mechanism; for example, Suri et al.[5] reported that it is insignificant at 200 °C and remarkably enhanced at 300 °C when tetrakis(dimethylamino)hafnium/H 2 O were used for HfO 2 deposition on GaAs. In conjunction with affecting the defective IL removal efficiency, the ALD temperature is also one of the important criteria in determining the final microstructural and electrical properties of the high-k films.Together with GaAs and InGaAs, InP is also a promising candidate as an alternative n-channel material, however, fewer works have been reported on the self-cleaning effect during the ALD high-k process on InP. Recently, an interesting IL evolution behavior showing a large dependence on the HfO 2 thickness was reported when tetrakis-(ethylmethylamino)hafnium (TEMAHf) and H 2 O were used on InP at an ALD temperature equal to or higher than 300 °C [6,7]. In these reports, largely insufficient selfcleaning was observed at an early stage and a continuous decrease of the IL occurred as the film thickness was increased, which is a quite different trend to that on GaAs or InGaAs, which shows a nearly complete removal of IL after only a few ALD cycles [2,4,5]. However, a detailed mechanism for this phenomenon was not given.On these grounds, we investigated the effect of the ALD temperature on the IL evolution during the HfO 2 formation on InP and tried to rationalize it by focusing on the temperature-dependent self-cleaning effect and possible simultaneous substrate oxidation during the ALD process. In addition, the film-thickness-dependent IL thickness variation was accounted for by other possible contributing factors.As substrates, (100)-oriented InP wafers with an n-type carrier concentration of (4−5) × 10 15 cm -3 were used. The substrates were successively cleaned by 1% HF and 21% (NH 4 ) 2 S diluted solutions. The ALD HfO 2 process was carried out in a cross-flow type ALD system at various substrate temperatures: 200, 250, and 300 °C. During each deposition cycle, TEMAHf and H 2 O were sequentially delivered with N 2 purging in between, and the total number The effects of both the deposition temperature and the HfO 2 film thickness on the interfacial layer (IL) evolution were studied when tetrakis(ethylmethylamino)hafnium and H 2 O based atomic layer deposition (ALD) was performed on InP substrates. While the self-cleaning effect resulted in an IL-free structure after formation of ~2 nm thick ...