Interface quality of atomic layer deposited La-doped ZrO2 films on Ge-passivated In 0.15 Ga 0.85 As substrates
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1194-A08-10
Interface quality of atomic layer deposited La-doped ZrO2 films on Gepassivated In0.15Ga0.85As substrates A. Molle1, G. Brammertz2, L. Lamagna1, S. Spiga1, M. Meuris2, M. Fanciulli1,3 1
Laboratorio Nazionale MDM, CNR-INFM, via C. Olivetti 2, I-20041 Agrate Brianza
(Milano), Italy 2 3
IMEC vzw, Kapeldreef 75, B-3001 Leuven, Belgium Dipartimento di Scienza dei Materiali, Università degli Studi di Milano Bicocca,
Milano, Italy
ABSTRACT La-doped ZrO2 thin films were grown by O3-based atomic layer deposition on III-V (GaAs, In0.15Ga0.85As) substrates. The direct oxide deposition and the insertion of a Ge passivation layer in between the oxide and the substrate are compared in terms of the resulting density of interface traps. An improved electrical quality of the Ge-passivated interfaces concerning the energy region close to the conduction band edge in the semiconductor band-gap is demonstrated through conductance maps at various temperatures and it is attributed to Ga-related interfacial defects.
INTRODUCTION GaAs and InxGa1-xAs (III-V compounds) are promising candidates for replacing Si as channel material in high-speed metal oxide semiconductor (MOS) based devices [1]. Among the main challenges to face the III-V integration is the III-V surface passivation which intrinsically correlates the electrical features with the chemical quality of the oxide/III-V interface. Native defects, such as bonding disruption, dangling bonds,
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formation of antisites, vacancies or interstitials, can be extrinsically induced upon MOS processing, e.g. oxidation-induced surface restructuring, oxide deposition, thermal effects [2-5]. As a consequence, trapping levels take place in the semiconductor bandgap which may pin the interface Fermi level thus impeding a correct MOS behavior [6,7]. The chemical counterpart of these defects can be tracked in the observation of interfacial semiconductor-oxygen or homopolar As-As bonding. Several solutions have been so far proposed to optimize the III-V interface quality, which can be summarized in: a) chemical approach, e.g. surface pre-treatments or interface self-cleaning by the atomic layer deposition (ALD) of Al2O3 stack [8,9]; b) epitaxial growth of the Ga-Gd-O gate oxide [10]; or c) intercalation of ultra-thin interface passivation layers (IPL) [11,12]. Our work reports on ALD grown La-doped ZrO2 (LZO) onto Si-doped (1x1017 cm-3) GaAs(001) and In0.15Ga0.85As(001) upon insertion of Ge IPLs. The latter substrate was fabricated by growing a 30 nm In0.15Ga0.85As film onto a GaAs support substrate via metal-organic chemical vapor deposition at 500°C. The substrates were chemically pretreated by 3 min long dipping in NH4(OH) solution (4%). 2 nm thick Ge layer was deposited at 20°C by an electron beam evaporator in a high-vacuum chamber. LZO films were subsequently grown in an ALD reactor at 300°C with O3 as oxidizing precursor, and [(iPrCp)3La] and [(MeCp)2ZrMe(OMe); also known as ZrD-04] as La and Zr metal precursors [13]. The use of O3 as oxidizing species explicitly addresses t
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