Correlation of Bandgap Reduction with Inversion Response in (Si)GeSn/High-k/Metal Stacks

Abstract

The bandgap tunability of (Si)GeSn group IV semiconductors opens a new era in Si-technology. Depending on the Si/Sn contents, direct and indirect bandgaps in the range of 0.4-0.8 eV can be obtained, offering a broad spectrum of both photonic and low power electronic applications. In this work, we systematically studied capacitance-voltage characteristics of high-k/metal gate stacks formed on GeSn and SiGeSn alloys with Sn-contents ranging from 0 to 14 at. % and Si-contents from 0 to 10 at. % particularly focusing on the minority carrier inversion response. A clear correlation between the Sn-induced shrinkage of the bandgap energy and enhanced minority carrier response was confirmed using temperature and frequency dependent capacitance voltage-measurements, in good agreement with k.p theory predictions and photoluminescence measurements of the analyzed epilayers as reported earlier. The enhanced minority generation rate for higher Sn-contents can be firmly linked to the bandgap reduction in the GeSn epilayer without significant influence of substrate/interface effects. It thus offers a unique possibility to analyze intrinsic defects in (Si)GeSn epilayers. The extracted dominant defect level for minority carrier inversion lies approximately 0.4 eV above the valence band edge in the studied Sn-content range (0-12.5 at. %). This finding is of critical importance since it shows that the presence of Sn by itself does not impair the minority carrier lifetime. Therefore, the continuous improvement of (Si)GeSn material quality should yield longer nonradiative recombination times which are required for the fabrication of efficient light detectors and to obtain room temperature lasing action.

Impact of Wet Treatments on the Electrical Performance of Ge0.9Sn0.1-Based p-MOS Capacitors

“…In the D1 case (Figure 5a), C−V curves are nearly flat, the dispersion in accumulation is high (12.3%) between 1 kHz and 1 MHz, and the flat band voltage shift is large, indicating a poor interface quality with the Al 2 O 3 layer. 36 Conversely, sample D8's C−V curves show a low dispersion of 3.3% in accumulation between 1 kHz and 1 MHz and a small frequency-dependent flat band voltage shift, indicating a very good Al 2 O 3 /Ge 0.9 Sn 0.1 interface quality 37,38 and highlighting the efficiency of the C8 cleaning procedure.…”

“…Indeed, according to the literature, the lowest D it reported until now for the Al 2 O 3 /GeSn interface is in the (2−5) × 10 12 cm −2 eV −1 range. 13,14,36 ■ CONCLUSION In summary, the impact of nine wet treatments prior to Al 2 O 3 deposition on Ge 0.9 Sn 0.1 layers was rigorously investigated. AFM showed the presence of Sn droplets on the degreased Ge 0.9 Sn 0.1 surface.…”

“…For instance, Gupta et al showed that the combination of an 1:1 HF:HCl wet cleaning followed by a H 2 O prepulsing yielded good C – V characteristics . Similar protocols were used by other groups. − Han et al showed interesting electrical performances in Ge 0.958 Sn 0.042 channel p-MOSFETs when a (NH 4 ) 2 S treatment was used prior to the ALD of high- k dielectrics . Nevertheless, the impact of wet treatments on the chemical and electrical behavior of interfaces was not systematically investigated on GeSn alloys with a Sn percentage above 8%.…”

Schottky barrier tuning via dopant segregation in NiGeSn-GeSn contacts

“…29 Recently, we experimentally demonstrated that minority carrier response in GeSn MOS-structures is significantly stronger than in Ge. 30 According to the above discussion, it should be pointed out that the following SBH-values always denote the effective SBH. This way, the hSBH was extracted for several intrinsically p-type GeSn alloys with Sn contents ranging from 3 at.…”

Improvement of the electrical performance of Au/Ti/HfO2/Ge0.9Sn0.1 p-MOS capacitors by using interfacial layers

“…2(b). The minority carrier generation times (s min ) were simulated in our model with the following expression: 27 studied the inversion response as a function of the Sn content in metal/high-k/GeSn MOS capacitors. They showed that higher Sn contents resulted in higher minority carrier generation times.…”