Inplane optical anisotropy of InAs/GaSb superlattices with alternate interfaces
 Shujie Wu^{1, 2},
 Yonghai Chen^{1, 2}Email author,
 Jinling Yu^{1, 2},
 Hansong Gao^{1, 2},
 Chongyun Jiang^{1, 2},
 Jianliang Huang^{3},
 Yanhua Zhang^{3},
 Yang Wei^{3} and
 Wenquan Ma^{3}
DOI: 10.1186/1556276X8298
© Wu et al.; licensee Springer. 2013
Received: 26 April 2013
Accepted: 16 June 2013
Published: 25 June 2013
Abstract
PACS
78.67.Pt, 78.66.Fd, 78.40.Fy
Background
CP energies (in eV) of bulk InAs, GaSb, GaAs, and InSb measured by S.Adachi [[10]]
InAs  GaSb  InSb  GaAs  

E _{0}  0.36  0.72  0.18  1.42 
E_{0} + Δ_{0}  0.76  1.46  0.99  1.77 
E _{1}  2.50  2.05  1.80  2.90 
E_{1}+ Δ_{1}  2.78  2.50  2.30  3.13 
E _{2}  4.45  4.00  3.90  4.70 
Methods
The InAs/GaSb SLs were grown on GaSb buffer layer, which is deposited on nonintentional doping GaSb (001) substrates by molecular beam epitaxy (MBE). The GaAslike IFs were generated by employing As soaking after GaSb is deposited. The InSblike IFs were formed by InSb deposition. Two samples have the same structure as 100 periods InAs (10 ML)/GaSb (8 ML) without capping layer. The difference of the two examples is only the thickness of InSb layer, 0.43 ML (sample A) and 1.29 ML (sample B), respectively. We used a Bede D1 highresolution Xray diffractometer to characterize structural quality of the samples. The lattice mismatch and oneperiod thickness can be predicted.
Here, α and β are complicated functions of four refractive indices and the wavelength of light. Both the real and imaginary part of Δ r/r are linear combinations of real and imaginary part of Δ ε[11]. The degree of polarization (DOP) is defined as $P=\frac{{M}_{110}{M}_{1\overline{1}0}}{{M}_{110}+{M}_{1\overline{1}0}}$ (M_{110} is the transition probability when light is polarized along [110] direction). Im(Δ ε) is proportional to Δ M, and Im(ε) is proportional to M. It can be deduced from the imaginary part of Δ ε and the imaginary part of ε: $\left(P=\frac{\mathit{\text{Im}}(\mathrm{\Delta \epsilon})}{2\mathit{\text{Im}}(\epsilon )}\right)$[12].
Results and discussion
Xray diffraction (XRD) results indicate that the range of 0th peak of sample A and the substrate is 0.367° and 0.151° for sample B. The full width at half maximum (FWHM) of the first satellite peak is 34 arcsec for sample A and 43 aresec for sample B. Both of the samples show compression strain. The calculated strain is 0.0054 for sample A and 0.0023 for sample B. Increasing the thickness of InSblike IF layers can reduce the average compression strain. We predicted oneperiod thickness from the spacing between the satellites. Each period thickness of sample A is 55.9 Å and 56.8 Å for sample B.
Varshni parameters for temperaturedependence fitting CPs of samples A and B
Sample  CPs  E_{ 0 }(eV)  α 10^{−4} (eVK^{−1})  β (K) 

A  CP1  2.218  5.34  149 
CP2  2.646  6.45  160  
CP3  2.888  8.08  235  
B  CP1  2.217  5.62  130 
CP2  2.666  6.44  198  
CP3  2.817  6.51  207 
Conclusions
The IPOA of InAs/GaSb SLs with InAslike and GaSblike alternate IFs were observed by RDS. The main mechanism can attribute to the symmetry reduction to C_{2v}. The increasing of InSb IFs’ thickness release the mismatch between the SL layer and substrate. The red shift of CP energies was observed. Meanwhile, the holes are further localized in the InSb IFs, leading to the intensities of IPOA further increased.
Abbreviations
 IPOA:

Inplane optical anisotropy
 SLs:

Superlattices
 RDS:

Reflectance difference spectroscopy
 CP:

Critical point
 IFs:

Interfaces
 NCA:

No common atom
 ML:

Monolayer
 MBE:

Molecular beam epitaxy
 DOP:

Degree of polarization.
Declarations
Acknowledgements
This work was supported by the 973 Program (2013CB632805, 2012CB921304 and 2010CB327602) and the National Natural Science Foundation of China (No. 60990313, No. 61176014, and No. 61290303).
Authors’ Affiliations
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