Extraction of large valence-band energy offsets and comparison to theoretical values for strained-Si/strained-Ge type-II heterostructures on relaxed SiGe substrates

• Main Authors: Teherani, James T. (Contributor), Chern, Winston (Contributor), Antoniadis, Dimitri A. (Contributor), Hoyt, Judy L. (Contributor), Ruiz, Liliana (Author), Poweleit, Christian D. (Author), Menendez, Jose (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science (Contributor)
• Format: Article
• Language: English
• Published: American Physical Society, 2012-07-12T18:18:56Z.
• Subjects: Article
• Online Access: Get fulltext

 Metal-oxide-semiconductor capacitors were fabricated on type-II staggered gap strained-Si/strained-Ge heterostructures epitaxially grown on relaxed SiGe substrates of various Ge fractions. Quasistatic quantum-mechanical capacitance-voltage (CV) simulations were fit to experimental CV measurements to extract the band alignment of the strained layers. The valence-band offset of the strained-Si/strained-Ge heterostructure was found to be 770, 760, and 670 meV for 35, 42, and 52% Ge in the relaxed SiGe substrate, respectively. These values are approximately 100 meV larger than the usually recommended band offsets for modeling Si/Ge structures. It is shown that the larger valence-band offsets found here are consistent with an 800-meV average valence-band offset between Si and Ge, which also explains the type-II band alignment observed in strained-Si[subscript 1−x]Ge[subscript x] on unstrained-Si heterostructures.