Abstract
In order to fulfill the performance requirements of future CMOS technologies beyond the 15 nm node, it is adamant to employ higher carrier mobility channel semiconductors such as III-V compound semiconductor GaAs plus high-k dielectrics. Nevertheless, a robust high-k oxide/GaAs interface with a low interfacial density of states (Dit) is needed to realize the inversion-channel III-V MOSFETs. In this work, a powerful technique of in-situ ALD-Al2O3 and MBE-GGO on GaAs approach without using interfacial passivation layers and chemical treatments between oxide/III-V interfaces were performed in a multi-chamber UHV system. By using in-situ process, both oxide/semiconductor hetero-structures showed very abrupt interface without interfacial layer was revealed by HR-TEM. The interfacial properties are investigated by high frequency (1kHz-1MHz), quasi-static (QS) capacitance-voltage (C-V) measurements and QS-CV calculations. By QS-CV calculations, the Dit distribution versus energy within the band gap can be extracted and is consistent with aforementioned high frequency C-V results between these two systems. The Dit distribution of ALD-Al2O3/GaAs has exhibited a peak around midgap with a value of ~8x1012 eV-1cm-2 and is much broaden and larger with a value ~2x1013 eV-1cm-2 after additional rapid thermal annealing at 850oC in He for 10s. On the other hand, a low Dit value of less than 1012 eV-1cm-2 is attained for the entire band gap for MBE-GGO/GaAs even with RTA at 850oC in He for 10s. Consequently, MBE-GGO is proper dielectric oxide for MOSFETs design due to effective passivation of GaAs surface without Dit peak around mid-gap and excellent thermodynamic stability after RTA to 850oC for S/D activation.