Abstract
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.
Highlights
resonant tunneling diodes (RTDs) epitaxy has been performed using both molecular beam epitaxy (MBE)5 and metalorganic vapor-phase epitaxy (MOVPE)6 reactors, but despite the outstanding precision of these techniques, the characterization processes present a range of issues leading, in turn, to difficulties in optimization of the epitaxial processes
To improve the reproducibility and the mass-manufacture of low-cost tunnel devices, we previously showed that low temperature PL spectroscopy provided a fast characterization technique,9
The InP/InGaAs/AlAs RTD structures described here were grown in a vertical Thomas close-coupled shower head MOVPE reactor on (100) semi-insulating InP:Fe substrates
Summary
RTD epitaxy has been performed using both molecular beam epitaxy (MBE)5 and metalorganic vapor-phase epitaxy (MOVPE)6 reactors, but despite the outstanding precision of these techniques, the characterization processes present a range of issues leading, in turn, to difficulties in optimization of the epitaxial processes. In combination with room temperature HR-XRD, line-shape fitting of the low temperature PL spectrum, and simulation, the observation of higher order optical transitions allows us to unambiguously determine the band-offsets and all key structural parameters of the RTD.
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