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Articles written in Pramana – Journal of Physics

• Γ andX bandgap hydrostatic deformation potentials for epitaxial In0.52Al0.48As on InP(001)

The pressure dependence of the direct and indirect bandgap of epitaxial In0.52Al0.48As on InP(001) substrate has been measured using photoluminescence up to 92 kbar hydrostatic pressure. The bandgap changes from Γ toX at an applied pressure of ∼ 43 kbar. Hydrostatic deformation potentials for both the Γ andX bandgaps are deduced, after correcting for the elastic constant (bulk modulus) mismatch between the epilayer and the substrate. For the epilayer we obtain$$(\Xi _d + \tfrac{1}{3}\Xi _u - a) as - (6 \cdot 92 + 0 \cdot 3) eV$$ and+(2.81±0.15)eV for the Γ andX bandgaps respectively. From the pressure dependence of the normalized Γ-bandgap photoluminescence intensity a Γ-X lifetime ratio, (τΓX), of 4.1×10−3 is deduced.

• Pressure-tuned resonance Raman scattering and photoluminescence studies on MBE grown bulk GaAs at theE0 gap

Hydrostatic pressure has been used to tune in resonance Raman scattering (RRS) in bulk GaAs. Using a diamond anvil cell, both the photoluminescence peak (PL) and the 2 LO and LO-phonon Raman scattered intensities have been monitored, to establish RRS conditions. When theE0 gap of GaAs matchesħωS orħωL, the 2 LO and LO-phonon intensity, respectively, exhibit resonance Raman scattering maxima, at pressures determined byħωL. With 647.1 nm radiation (ħωL = 1.916 eV), a sharp and narrow resonance peak at 3.75 GPa is observed for the 2 LO-phonon. At this pressure the 2 LO-phonon goes through its maximum intensity, and falls right on top of the PL peak, revealing thatħωS(2 LO) =E0. This is the condition for “outgoing” resonance. Experiments with other excitation energies (ħωL) show, that the 2 LO resonance peak-pressure moves to higher pressure with increasingħωL, and the shift follows precisely theE0 gap. Thus, the 2 LO RRS is an excellent probe to follow theE0 gap, far beyond the Γ-X cross-over point. A brief discussion of the theoretical expression for resonance Raman cross section is given, and from this the possibility of a double resonance condition for the observed 2 LO resonance is suggested. The LO-phonon resonance occurs at a pressure whenħωLE0, but the pressure-induced transparency of the GaAs masks the true resonance profile.

• # Pramana – Journal of Physics

Volume 95, 2021
All articles
Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019