Beneficial effect of La on band offsets in Ge/high-κ insulator structures with GeO2 and La2O3 interlayers

Abstract

The electron energy band alignment between (100)Ge and high-κ oxide insulators (ZrO2,Gd2O3,La2Hf2O7) grown by the atomic beam deposition method is analyzed using photoemission of electrons from the Ge valence band. Formation of a thin GeO2 passivation layer before the high-κ deposition is found to significantly reduce the barrier for electrons. However, when La2O3 is deposited as an interlayer, it strongly reacts with the Ge substrate to form a La–Ge–O germanate at the interface, which is found to retain a high barrier for the carriers in Ge.

Electron Band Alignment at Interfaces of Semiconductors with Insulating Oxides: An Internal Photoemission Study

“…By contrast, the absence of any measurable shift of the hole IPE threshold indicates the same CB position of Si and Ge with respect to the reference level of the oxide VB top. The spectra shown in Figure 17 also reveal a much reduced signal from the ILassisted electron IPE which reflects a transformation of the IL from GeO into a wide-gap La germanate which allows one to suppress low-field electron injection in the oxide stack [112,113]. Among other methods enabling reduction of the Ge oxidation one may mention the Ge surface passivation with several monolayers of silicon or using a GeN barrier layer [114,115].…”

“…In all these cases no IL-sensitive or crystallographic face related variations of the Si/high-oxide band offsets have been found affirming the behavior earlier found at interfaces of silicon with insulating metal oxides. Summarizing the available results regarding band offsets at the interfaces of Ge with insulating metal oxides [106][107][108][109][110][111][112][113][114][115][116][117][118], the energies of the oxide VB and CB edges are shown in…”

O 3 -based atomic layer deposition of hexagonal La2O3 films on Si(100) and Ge(100) substrates

“…37,38 Conversely, the spread regarding the methods for La 2 O 3 deposition on Ge substrates is narrower since the majority of published work is predominantly concerned with La 2 O 3 growth by electron beam evaporation 20,21 and molecular beam deposition. 24,[27][28][29]31 Nonetheless, it is widely acknowledged that atomic layer deposition ͑ALD͒ is the key tool to deposit innovative materials for fabricating a range of emerging nanostructures and nanodevices because it provides the capability to grow smooth and conformal films at relatively low temperatures and on large areas with an extremely accurate thickness control. 39 43 La͑ i PrCp͒ 3 is an interesting ALD precursor due to its relatively high vapor pressure ͑i.e., good volatility͒ stemming from the bulky alkyl group addition to the Cp ring.…”

“…Recently, lan-thanum germanate La x Ge y O z ͑LaGeO͒, which is almost unavoidably formed due to a strong and spontaneous reaction when La 2 O 3 comes in contact with the Ge surface, 24 has emerged as an attractive choice for high-k / Ge interfaces because of its beneficial role in defects passivation [24][25][26] and band offset enhancement. 27 Indeed, an intense effort within the Ge-based CMOS community is currently underway to optimize the properties of the ZrO 2 / La 2 O 3 stacks because preliminary work [27][28][29][30][31] has demonstrated encouraging electrical characteristics including a large potential for stack EOT scalability below 1 nm.…”

Oxidation-induced electron barrier enhancement at interfaces of Ge-based semiconductors (Ge, Ge1−xSnx, SiyGe1−x−ySnx) with Al2O3

“…Rather, the impact of the O3 oxidation through the 1-nm Al2O3 resembles the effect of other group III elements (La, Y, Sc) which consists in elimination of narrow-gap Ge suboxides through formation of wide-gap ILs [16][17][18]. Indeed, the earlier presented structural characterization results [9,10] indicate significant overlap of elemental profiles of Al and Ge over depth scale comparable to the thickness of the ALD-grown alumina film (5 nm).…”