AVS 56th International Symposium & Exhibition
    Applied Surface Science Tuesday Sessions
       Session AS-TuP

Paper AS-TuP3
Crossing of the E2, E2+Δ2, E2' and E2' + Δ2' CPs in InAsxSb1-x Alloys as Determined by Spectroscopic Ellipsometry

Tuesday, November 10, 2009, 6:00 pm, Room Hall 3

Session: Applied Surface Science Poster Session
Presenter: J.J. Yoon, Kyung Hee University, Korea
Authors: J.J. Yoon, Kyung Hee University, Korea
T.J. Kim, Kyung Hee University, Korea
S.Y. Hwang, Kyung Hee University, Korea
Y.J. Kang, Kyung Hee University, Korea
D.E. Aspnes, Kyung Hee University, Korea and North Carolina State University
Y.D. Kim, Kyung Hee University, Korea
H.J. Kim, Academia Sinica, Taiwan and University of Illinois at Urbana-Champaign
Y.C. Chang, Academia Sinica, Taiwan and University of Illinois at Urbana-Champaign
J.D. Song, Korea Institute of Science and Technology, Korea
Correspondent: Click to Email
Owing to its small band gap, HgxCd1-xTe is the dominant material for infrared (IR) detectors. However, due to the high Hg vapor pressures needed during growth, accurate compositions x are difficult to obtain, particularly over large areas. The low-bandgap III-V ternary alloy InAsxSb1-x exhibits important advantages, including better control of composition during growth, higher electron and hole mobilities, and the availability of high-quality, low-cost substrates. As a result, InAsxSb1-x alloys have recently been used to fabricate various IR optoelectronic devices. Although the optical properties and main critical-point (CP) energies of the binary endpoints InAs and InSb are well known, much less information is available for alloys of arbitrary x. Here, we report pseudodielectric function <ε> = <ε1> + i<ε2> data from 1.5 to 6.0 eV of InAsxSb1-x alloys for selected values of x over the entire composition range, assessing the removal of overlayers in real time to ensure that overlayer artifacts are minimized and therefore, that the data most closely represent the intrinsic dielectric responses e of these materials. Energies of the E1, E1 + Δ1, E0', E0' + Δ0', E2, E2 + Δ2, E2', E2' + Δ2', and E1' critical points (CPs) were obtained from numerically calculated second derivatives, and identified where necessary by band-structure calculations done using the linear augmented Slater-type orbital method (LASTO). The calculated CP energies agree well with those obtained from data, confirming the validity of the calculations. These calculations show a crossing of the E2, E2 + Δ2, E2', and E2' + Δ2' CP structures with increasing As-composition. Also, the band-structure calculations allow us to identify the InSb structures at 3.31 and 3.75 eV with the Δ5cu - Δ5vu and Δ5cl - Δ5vu saddle points at k = (0.35, 0, 0). These saddle points were reported previously only at low temperature. Our results will be useful in a number of contexts, including the design of optoelectronic devices based on InAsSb and obtaining a more detailed understanding of the band structure of these and related alloys.