Pressure-tuned resonance Raman scattering and photoluminescence studies on MBE grown bulk GaAs at theE
0 gap |
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Authors: | A Jayaraman G A Kourouklis R People S K Sputz L Pfeiffer |
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Institution: | (1) AT&T Bell Laboratories, 600 Mountain Avenue, 07974 Murray Hill, NJ, USA;(2) Present address: School of Technology, Physics Division, Aristotle University of Thessaloniki, Thessaloniki, Greece |
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Abstract: | 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 theE
0 gap of GaAs matchesħω
S orħω
L, the 2 LO and LO-phonon intensity, respectively, exhibit resonance Raman scattering maxima, at pressures determined byħω
L. With 647.1 nm radiation (ħω
L = 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 thatħω
S(2 LO) =E
0. This is the condition for “outgoing” resonance. Experiments with other excitation energies (ħω
L) show, that the 2 LO resonance peak-pressure moves to higher pressure with increasingħω
L, and the shift follows precisely theE
0 gap. Thus, the 2 LO RRS is an excellent probe to follow theE
0 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 whenħω
L ≈E
0, but the pressure-induced transparency of the GaAs masks the true resonance profile. |
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Keywords: | Pressure-tuning resonance Raman scattering semiconductors |
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