Enhanced B doping in CVD-grown GeSn:B using B d-doping layers

• Published in: Journal of crystal growth Vol. 483; p. 285
• Main Authors: Kohen, David, Vohra, Anurag, Loo, Roger, Vandervorst, Wilfried, Bhargava, Nupur, Margetis, Joe, Tolle, John
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier BV 01.02.2018
• Subjects: Chemical vapor deposition; Compressive properties; Doping; Germanium; Strain; Thickness; Tin
• ISSN: 0022-0248; 1873-5002

Highly doped GeSn material is interesting for both electronic and optical applications. GeSn:B is a candidate for source-drain material in future Ge pMOS device because Sn adds compressive strain with respect to pure Ge, and therefore can boost the Ge channel performances. A high B concentration is required to obtain low contact resistivity between the source-drain material and the metal contact. To achieve high performance, it is therefore highly desirable to maximize both the Sn content and the B concentration. However, it has been shown than CVD-grown GeSn:B shows a trade-offbetween the Sn incorporation and the B concentration (increasing B doping reduces Sn incorporation). Furthermore, the highest B concentration of CVD-grown GeSn:B process reported in the literature has been limited to below 1 x 1020 cm-3. Here, we demonstrate a CVD process where B δ-doping layers are inserted in the GeSn layer. We studied the influence of the thickness between each δ-doping layers and the δ-doping layers process conditions on the crystalline quality and the doping density of the GeSn:B layers. For the same Sn content, the δ-doping process results in a 4-times higher B doping than the co-flow process. In addition, a B doping concentration of 2 x 1021 cm-3 with an active concentration of 5 x 1020 cm-3 is achieved.