Photoluminescence excitation spectroscopy (PLE) and high-resolution x-ray diffraction (HR-XRD) are used to characterize the structural and electronic properties of high current density InGaAs/AlAs/InP resonant tunneling diode wafer structures. The non-destructive assessment of these structures is challenging, with several unknowns: well and barrier thickness, the well indium molar fraction, and band-offsets, which are a function of strain, material, growth sequence, etc. The low temperature PL spectra are deconvoluted through simulation and are shown to include contributions from type I (e1–hh1) and type II (conduction band–hh1) transitions that are broadened due to interface fluctuations on a range of length scales. PLE data are obtained by a careful choice of the detection wavelength, allowing the identification of the e2hh2 transition that is critical in determining the band-offsets. An agreement between the HR-XRD data, the PL, and the PLE data is only obtained for a given conduction band offset of 58.8%. This scheme, combining HR-XRD, PL, and PLE, consequently provides crucial electronic and structural information non-destructively.

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.

We investigated the difference between a macro scale PL and μPL (excitation and detection area ≤ 5µm 2 ). Lowtemperature 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 1μm 2 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.

Low-temperature micro-photoluminescence (μPL) is used to evaluate wafer structural uniformity of current densities >5mA/µm 2 InGaAs/AlAs/InP resonant tunnelling diode (RTD) structures on different length scales. Thin, highly strained quantum wells (QWs) are subject to monolayer fluctuations, leading to a large statistical distribution in their electrical properties. This has an important impact on the RTD device performance and manufacturability. The PL spot size is reduced using a common photolithography mask to reach a typical high Jpeak for a given RTD mesa size (1 ~ 100 µm 2 ). We observe that for lower strain-budget samples, that the PL line-shape is essentially identical for all excitation/collection areas. For higher strain-budget samples, there is a variation in the PL line-shape that is discussed in terms of a variation in long-range disorder brought about by strain relaxation processes. The RTD operating characteristics are discussed in light of these findings, and we conclude that strain model limits overestimate the strain budget that can be incorporated in these devices. We also highlight μPL as a powerful non-destructive characterization method for RTD structures.There is a lack of efficient high-speed technology able to satisfy the ever-growing wireless datademand [1,2]. As a consequence, the THz frequency range (0.1-10THz)[3] has attracted considerable interest as it offers the wide bandwidth required for high data-rate communications. Resonant tunneling diodes (RTDs ) have been demonstrated to be the fastest solid-state device with oscillation near 2 THz [4] with highly attractive characteristics: tunability, compact dimensions, and room temperature operation [5] . As for all quantum-effect devices [6], the RTD performance is critically dependent on crystal purity and heterointerface perfection. We previously demonstrated how ~80% of the parasitic valley current is associated with non-thermal inelastic scattering [7], and as a consequence, the RTD output power is limited by crystal-related imperfections.RTDs are composed of a single double-barrier QW generally growth by molecular beam epitaxy (MBE) or metal-organic vapor-phase epitaxy (MOVPE), despite the outstanding precision offered by these technologies, wafer characterization remains a difficult process, leading to knowledge barriers in

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