Low-temperature photoluminescence spectroscopy (PL) and excitation spectroscopy(PLE) are used to characterize and compare high current density resonant tunnelling diodes (RTD) structures. RTD structural characteristics are detected using X-Ray diffraction (XRD) while the electrical characteristics are detected by PL and PLE. Results are used to link the structure electrical properties to the RTD device IV characteristic. We started focusing the attention on the first quasi bound state (e1) energy, fundamental for the RTD operation. PL is used to detect the TypeI and Type II QW radiative transitions. The e1 state is obtained by the difference between the Type I (e1–hh1) and type II (conduction band–hh1) transitions. PLE is consequently used to detect the e2-hh2 transition from which we characterize the energy of the e2 state and its position with respect to the e1 state. Experimental data are confirmed by the RTDs device IV characteristics. We highlight the combination PL and PLE as a powerful, fast, and non-destructive characterization method to link wafer properties and device performance in RTD structures.
We investigated the difference between a macro scale PL and μPL (excitation and detection area ≤ 5μm2). Low-temperature micro-photoluminescence (μPL) is used to evaluate structural perfection of high current density InGaAs/AlAs/InP resonant tunnelling diodes (RTD) structure on different length scales. The thin and highly strained quantum wells (QWs) is subject to monolayer fluctuations in well and barrier thickness that can lead to random fluctuations in their band profile. μPL is performed reducing the laser spot size using a common photolithography mask to reach typical RTD mesa size (a few square microns). We observed that for spot size around 1μm2 the PL line shape present strong differences on multiple points on the wafer. These variations in the PL is investigated by line-shape fitting and discussed in terms of variations in long-range disorder brought about by strain relaxation processes. We also highlight this μPL as a powerful and cost-effective non-destructive characterization method for RTD structures.
High-resolution X-ray diffraction (HR-XRD), and low-temperature photoluminescence spectroscopy (LT-PL) are used to investigate the structural properties and inhomogeneities of high current density InGaAs/AlAs/InP resonant tunnelling diode (RTD) wafer structures. The non-destructive assessment of these structures is challenging, with structural variables: well and barriers thickness and the well indium molar fraction, in addition to electronic variables such as the band-offsets being functions of strain, growth sequence, etc.. Experimental PL data are compared with simulations allowing the deconvolution of the PL spectra, that includes Type I and Type II transitions broadened by interface fluctuations on length scales smaller and much larger than the exciton. This method provides details of the non-uniformity of the epitaxial material nondestructively.
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