| AVS 56th International Symposium & Exhibition | |
| Applied Surface Science | Tuesday Sessions |
| Session AS-TuP |
| Session: | Applied Surface Science Poster Session |
| Presenter: | Y.W. Jung, Kyung Hee University, Korea |
| Authors: | Y.W. Jung, Kyung Hee University, Korea T.H. Ghong, Kyung Hee University, Korea J.S. Byun, Kyung Hee University, Korea S. Kim, Kyung Hee University, Korea Y.H. Cha, Kyung Hee University, Korea 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 S.H. Shin, Korea Institute of Science and Technology, Korea J.D. Song, Korea Institute of Science and Technology, Korea |
| Correspondent: | Click to Email |
We present pseudo dielectric function data <ε> = <ε1> + i<ε2> from 0.7 to 5.0 eV of oxide-free AlSb at 300 K that is currently the most accurate representation of the bulk dielectric response ε of the material. The data were obtained by in-situ spectroscopic ellipsometry (SE). SE is a well-known method of obtaining <ε> directly, without requiring Kramers-Kronig analysis. AlSb is an important material for optoelectronic applications such as infrared optical devices and high-electron-mobility transistors. However, because overlayers strongly affect <ε> and Al reacts readily with oxygen, the approximate determination of ε of any Al-containing semiconductor ordinarily requires complex processing to minimize overlayer artifacts. We avoid this by using in situ SE to obtain <ε> data before oxides have the opportunity to form.
Our measurements were done on an AlSb film d = 1.5 mm thick that was grown on a GaAs (001) substrate using molecular beam epitaxy (MBE). Since d is significantly larger than the critical thickness of AlSb, the film is fully relaxed and its measured dielectric properties closely approximate those of bulk material. The growth station features an integrated spectroscopic ellipsometer. Measurements were made through strain-free windows while maintaining the AlSb layer in ultrahigh vacuum. In the interference-oscillation region, ε was extracted with a multilayer parametric model. Compared to previously reported results, our <ε2> data show lower and higher values in the E1 and E2 spectral regions, respectively, confirming that our data are less affected by overlayers. We also observe the indirect band gap of AlSb, and obtain the E0, E0 + Δ0, E1, E1 + Δ1, E0', E0' + Δ0', E2, and E2 + Δ2 critical-point (CP) energies from numerically calculated second derivatives. Band-structure calculations done using the linear augmented Slater-type orbital (LASTO) method were performed to identify overlapping CPs in the E2 energy region. The calculated CP energies agree well with those obtained from data, confirming the validity of the calculations. Our results will be useful in various contexts, including the design of optoelectronic devices.