Temperature dependent electronic band structure of wurtzite GaAs nanowires

Abstract

It has recently become possible to grow GaAs in the wurtzite crystal phase. This ability allows interesting tests of band-structure theory. Wurtzite GaAs has two closely spaced direct conduction bands as well as three nondegenerate valence bands. The energies of the band edges are not well known, in particular not as a function of temperature. In order to improve the accuracy we have studied the temperature dependence of the conduction band minimum as well as of the second valence band maximum using resonant Raman scattering (of up to 3LO Raman lines). We find that the temperature dependence of the bandgap in wurtzite GaAs is very similar to that in zinc blende GaAs. Our results show that they have the same band gaps not only at 7 K but also at room temperature to within 5 meV. This is in some discrepancy with previous work. We find that the energy difference between the first two Γ and Γ valence bands is constant, around 100 meV, over the investigated temperature range, 7 K to 300 K. Due to a fortuitous spacing of the energy bands we find a very unexpected and strong quadruple resonance in the resonant Raman scattering.

Wurtzite AlGaAs Nanowires

“…Our nanowires show pronounced emission at room temperature, even though the intensity drops in the range 200-300 K. The wavelength of emission does not have a noticeable change in the temperature range from 2 K to about 100 K, and undergoes a red-shift at higher temperatures. This behavior is expected from the Varshni empirical equation for the temperature dependence of semiconductor bandgaps 26 and is similar, for instance, to the wurtzite GaAs 22 . The measurements at low temperatures (2-50 K) show a notched spectrum, composed of several sharp features, that we attribute to bright emission from crystal-phase structures collected during the scan at these temperatures.…”

Temperature dependence of optical properties of InAs/InP quantum rod-nanowires grown on Si substrate

“…The best fitting parameters for the two models are summarized in Table 3 along with parameters from the literature. These parameters are closed to the values reported in the literature for ZB InAs which indicates that ZB and WZ InAs have similar thermal parameters as observed for InP [47,54] and GaAs [55] (even if there is some discrepancy for this semiconductor materiel [56]). The low temperature data points (<100 K) are systematically below the Varshni curves by about 5 meV.…”

Correlated Nanoscale Analysis of the Emission from Wurtzite versus Zincblende (In,Ga)As/GaAs Nanowire Core–Shell Quantum Wells

“…This is a significant finding, as an interpolation of the experimentally-observed band gaps in binary alloys would predict a shift of only 10 meV in unstrained In 0.15 Ga 0.85 As. 23,24,28 However, for an In content of 15%, the ternary QWs experience a compressive strain of about 1.1% from the lattice mismatch with the GaAs core and outer shell. The opposing impact of this strain on the valence band energies in WZ and ZB (In,Ga)As accounts for the remaining shift in energy.…”