Effect on Al:MO2/In0.53Ga0.47As interface (M = Hf, Zr) of trimethyl-aluminum pre-treatment during atomic layer deposition

Abstract

For the fabrication of n-type metal–oxide–semiconductor field-effect transistor based on high mobility III–V compound semiconductors as channel materials, a major requirement is the integration of high quality gate oxides on top of the III–V substrates. A detailed knowledge of the interface between the oxide layer and the substrate is mandatory to assess the relevance of interdiffusion and related defects, which are detrimental. Here we grow high dielectric constant (k) Al:MO2 (M=Hf, Zr) gate materials on In0.53Ga0.47As substrates by atomic layer deposition, after an Al2O3 pre-treatment based on trimethylaluminum is performed to properly passivate the substrate surface. Time of flight secondary ion mass spectrometry depth profiles reveal not only the film integrity and the chemical composition of the high-k oxide but also well elucidate the effect of the Al2O3 pre-treatment on Al:MO2/In0.53Ga0.47As interface. Even though the chemical profile is well defined in both cases, a broader interface is detected for Al:ZrO2. X-ray photoemission spectroscopy evidenced the presence of As3+ states in Al:ZrO2 only. Accordingly, preliminary capacitance–voltage measurements point out to a better field effect modulation in the capacitor incorporating Al:HfO2. Based on the above considerations Al:HfO2 looks as a preferred candidate with respect to Al:ZrO2 for the integration on top of In0.53Ga0.47As substrates.