Temperature-dependent direct transition energy in Ge0.99Sn0.01 film grown on Si measured by photoreflectance spectroscopy

Jo, Hyun-Jun; So, Mo Geun; Kim, Jong Su; Ryu, Mee‐Yi; Yeo, Y. K.; Kouvetakis, John

doi:10.1016/j.tsf.2015.06.008

Cited by 13 publications

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References 35 publications

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“…The final residual tensile strain value was estimated to be 0.20% according to HRXRD measurement. More detailed descriptions of Ge 1-y Sn y crystal growth and annealing temperatures can be found from references [9] and [23], and those of RBS and HRXRD measurements can be obtained from references [23] and [24]. PR measurements were performed using a 637 nm laser diode as an excitation source with the excitation intensity of 400 mW/cm 2 , and the PR signals were detected by an extended InGaAs detector (1,000-2,400 nm).…”

Section: Methodsmentioning

confidence: 99%

Observation of temperature-dependent heavy- and light-hole split direct bandgap and tensile strain from Ge0.985Sn0.015 using photoreflectance spectroscopy

Kim

et al. 2016

Current Applied Physics

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Temperature-(T-) dependent photoreflectance (PR) measurements have been made for the tensile-strained, undoped Ge 0.985 Sn 0.015 film grown on n-Si substrate by ultra-high vacuum chemical vapor deposition method. The PR spectra at room temperature consist of two signals at around 0.739 and 1.022 eV, which are assigned to the direct transitions from conduction Γ valley to valence and spin-orbit split-off bands, respectively. The T-dependent PR measurements show tensile-strain split direct bandgap transitions from the Γ valley to the light-hole (E LH) and heavy-hole (E HH) bands at energies of 0.772 and 0.803 eV at 12 K, respectively, which are not usually observable from the photoluminescence measurements for relatively high Sn content Ge 1-y Sn y samples. The PR signals for both HH and LH bands are blue shifted and their intensities decrease with increasing temperature, but both LH and HH PR signals persist through 240 K and only one HH PR signal is observed at room temperature. It has been observed that the separation energy between the E HH and E LH increases as T decreases, which clearly indicates an increase in tensile strain as T decreases. From the analysis of the T-dependent separation energy between the E LH and E HH , the T-dependent tensile strain in the Ge 0.985 Sn 0.015 film was obtained, which might not be easily measured using the X-ray diffraction method.

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