Far Infrared Spectroscopy of Semiconductors at Large Hydrostatic Pressures

Abstract

The combination of high resolution far infrared spectroscopy and large hydrostatic pressures produced by diamond anvil cells (DAC) offers a unique approach to the study of dopants, defects, and bandstructure related properties of semiconductors. The problem of small optical throughputs typical of DACs has been solved. Using this unique tool, we have obtained several new results, including the discovery of a local vibrational mode of the DX center in GaAs: Si and the demonstration that the DX center is a negativeU defect. We have also discovered the first evidence of DX centers in InP and studied the ground to bound excited state transitions of shallow impurities in GaAs at pressures at which GaAs is an indirect bandgap semiconductor with its conduction band minimum near the X symmetry point. I ) Mailstop 2-200,

Revealing the Origin of Luminescence Center in 0D Cs4PbBr6 Perovskite

“…We further argue that the observed pressure responses of PL and Raman cannot be explained by Br vacancies or other lead halide structures such as Cs 2 PbBr 4 . The effect of hydrostatic pressure on point-defect states or luminescent centers has been investigated in many semiconductors. − The consensus is that localized states such as Br vacancies are very stable under hydrostatic pressure, especially if they are already deep level states. First, their optical activity will remain more or less the same and certainly will not disappear suddenly as long as its host material maintains the same structure.…”

“…We further argue that the observed pressure responses of PL and Raman cannot be explained by Br vacancies. The effect of hydrostatic pressure on point-defect states or luminescent centers has been investigated in many semiconductors 51,52,53,54,55,56 . The consensus is that localized states such as Br vacancies are very stable under hydrostatic pressure, especially if they are already deep level states.…”

CsPbBr3@Cs4PbBr6 Emitter-in-Host Composite: Fluorescence Origin and Interphase Energy Transfer

“…Unambiguously, the strict synchronization between the PL and Raman signals indicates a strong association between the fluorescence and the CsPbBr 3 impurity in 0D HP. Moreover, the authors also excluded the Br vacancy as an emissive center, because, according to the consensus in many semiconductors, a Br vacancy is highly stable under hydrostatic pressure, especially when as a deep-level defect. − Given this precondition, if Br is the emitter of the fluorescence or contributes to the fluorescence: (i) the PL signal should be maintained, more or less, as long as the host material is still able to handle the pressure rather than disappear at ∼2 GPa; (ii) the pressure-induced energy shift in fluorescence should be less than that of the host bandgap. However, the bandgap of Cs 4 PbBr 6 decreases only by 10 meV under 1 GPa, but the observed PL shift reaches 20 meV, which is twice the bandgap shift.…”

Extrinsic Green Photoluminescence from the Edges of 2D Cesium Lead Halides

“…More importantly, these observations have helped us to rule out the alternative theory of defect states due to the following reasons. For localized states such as vacancies, their state depends on the host media and their transition energy should be weakly depending on the change of host's bandgap [54][55][56][57][58][59] . In other words, The high quality of CsPb 2 Br 5 platelets and possible attachment of CsPbBr 3 nanocrystals to their surfaces is due to their different solution growth conditions and drying process.…”