arXiv subjects

Leland Nordin

Publications and source records attributed to Leland Nordin.

6 recordsLinked to original sources

arXiv2026

Heteroepitaxial Growth of PbSe on InP Substrates via Lattice-Matched III-V Buffer Layers

Detector cost remains a barrier to the widespread adoption of mid-wave infrared (3-5 micron) technology. PbSe, an inexpensive narrow band gap IV-VI semiconductor that has been used since the early 1940s, delivers high performance for infrared detection despite the abundance of grain boundaries in polycrystalline films. Epitaxial growth, however, could provide superior crystalline quality and interfaces, but suitable substrates remain limited for PbSe. Recent PbSe heteroepitaxy has focused primarily on III-V, II-VI and group-IV substrates that each offer a comparatively narrow range of lattice-matched alloys for heterostructure engineering. Here we show that InP-based heteroepitaxy provides access to a broader materials platform while limiting the lattice mismatch with PbSe to approximately 4%. We grow 150-nm thick PbSe films by molecular beam epitaxy on 200-nm thick In0.53Ga0.47As and In0.52Al0.48As buffers on (001) InP substrates. Reflection high-energy electron diffraction and X-ray diffraction show (001)-oriented rock-salt PbSe with an out-of-plane lattice constant of 6.12 Angstrom on both buffers. Photoluminescence (PL) is observed from room-temperature down to 12 K and the peak wavelength red-shifts from 3.7 to 5.0 microns. Under identical measurement conditions, the room-temperature peak PL intensities from films on In0.53Ga0.47As and In0.52Al0.48As are approximately 1.9x and 1.3x that of a PbSe on GaAs substrate reference, respectively. These results establish an InP-compatible platform for integrating narrow band-gap PbSe with a broad range of ternary and quaternary III-V alloys, including, for example, structures in which In0.53Ga0.47As serves as both a short-wave infrared absorber and a template for PbSe growth.

cond-mat.mtrl-sci↗

arXiv2026

Mid-infrared LEDs based on lattice-mismatched hybrid IV-VI/III-V heterojunctions

Light-emitting diodes (LEDs) can bridge the gap between narrow linewidth, expensive lasers and broadband, inefficient thermal globars for low-cost chemical sensing in the mid-infrared (mid-IR). However, the efficiency of III-V based mid-IR LEDs at room temperature is low, primarily limited by strong nonradiative Auger-Meitner recombination that is only partially overcome with complex quantum-engineered active regions. Here, we exploit the intrinsically low Auger Meitner recombination rates of the IV-VI semiconductors PbSe and PbSnSe, while leveraging the mature III-V platform through the fabrication of hybrid heterojunctions that mediate the ~8% lattice mismatch to GaAs. Electrically injected n-PbSe/p-GaAs LEDs emit at 3.8 um with output powers up to 400 uW under pulsed operation and a peak wall plug efficiency of 0.08% at room temperature, approaching the performance of commercial III-V LEDs at similar wavelengths. Incorporating 7% Sn extends the emission to 5 um in GeSe/PbSnSe/GaAs LEDs with output powers up to 45 uW. Notably, both devices operate despite threading dislocation densities on the order of 1e9/cm^2, underscoring the potential of hybrid IV-VI/III-V heterojunction architectures. We show that combining the complementary advantages of IV-VI and III-V semiconductors offers a simple and efficient mid IR optoelectronic platform for a rapidly expanding set of applications.

cond-mat.mtrl-sci↗

arXiv2025

Epitaxial PbGeSe thin films and their photoluminescence in the mid-wave infrared

PbSe is a narrow bandgap IV-VI compound semiconductor with application in mid-wave infrared optoelectronics, thermoelectrics, and quantum devices. Alkaline earth or rare earth elements such as Sr and Eu can substitute Pb to widen the bandgap of PbSe in heterostructure devices, but they come with challenges such as deteriorating optical and electronic properties, even in dilute concentrations due to their dissimilar atomic nature. We substitute Pb instead with column-IV Ge and assess the potential of rocksalt phase PbGeSe as a wider bandgap semiconductor in thin films grown by molecular beam epitaxy on GaAs substrates. Low sticking of GeSe adatoms requires synthesis temperatures below 260 °C to incorporate Ge, but this yields poor structural and compositional uniformity as determined by X-ray diffraction. Consequently, as-grown films in the range Pb0.94Ge0.06Se to Pb0.83Ge0.17Se (6-17% Ge) show much less bandgap widening in photoluminescence than prior work on bulk crystals using absorption. We observe that post-growth rapid thermal annealing at temperatures of 375-450 °C improves the crystal quality and recovers bandgap widening. Rapid interdiffusion of Ge during annealing, however, remains a challenge in harnessing such PbGeSe materials for compositionally sharp heterostructures. Annealed 17%-Ge films emit light at 3-3.1 um with minimal shift in wavelength versus temperature. These samples are wider in bandgap than PbSe films by 55 meV at room temperature and the widening increases to 160 meV at 80 K, thanks to sharply different dependence of bandgap on temperature in PbSe and PbGeSe.

cond-mat.mtrl-sci↗

arXiv2024

Expanded stability of layered SnSe-PbSe alloys and evidence of displacive phase transformation from rocksalt in heteroepitaxial thin films

Bulk PbSnSe has a two-phase region or miscibility gap as the crystal changes from a Van der Waals-bonded orthorhombic 2D layered structure in SnSe-rich compositions to the related 3D-bonded rocksalt structure in PbSe-rich compositions with large contrast in the electrical, optical, and thermal properties across this transition. With an aim to understand and harness this transition in thin films devices, we epitaxially integrate PbSnSe on GaAs by molecular beam epitaxy using an in-situ PbSe surface treatment and show a significantly reduced two-phase region by stabilizing the Pnma layered structure out to Pb$_{0.45}$Sn$_{0.55}$Se, beyond the bulk-limit of Pb$_{0.25}$Sn$_{0.75}$Se. Pushing further, we directly access metastable two-phase epitaxial films of layered and rocksalt grains that are nearly identical in composition around Pb$_{0.5}$Sn$_{0.5}$Se and entirely circumvent the miscibility gap. We present microstructural evidence for an incomplete displacive transformation from rocksalt to layered structure in these films that we speculate occurs during the sample cool down to room temperature after synthesis. In situ temperature-cycling experiments on a Pb$_{0.58}$Sn$_{0.42}$Se rocksalt film reproduce characteristic attributes of a displacive transition and show a modulation in electronic properties. We find well-defined orientation relationships between the phases formed and reveal unconventional strain relief mechanisms involved in the crystal structure transformation, using transmission electron microscopy. Overall, our work adds a scalable thin film integration route to harnessing the dramatic contrast in material properties in PbSnSe across a potentially ultrafast structural transition.

cond-mat.mtrl-sci↗

arXiv2021

Ultra-Thin All-Epitaxial Plasmonic Detectors

We present an infrared photodetector leveraging an all-epitaxial device architecture consisting of a 'designer' plasmonic metal integrated with a quantum-engineered detector structure, all in a mature III-V semiconductor material system. Incident light is coupled into surface plasmon-polariton modes at the detector/'designer' metal interface, and the strong confinement of these modes allows for a sub-diffractive ($\sim λ_0 / 33$) detector absorber layer thickness, effectively decoupling the detector's absorption efficiency and dark current. We demonstrate high-performance detectors operating at non-cryogenic temperatures (T = 195 K), without sacrificing external quantum efficiency, and superior to well established and commercially-available detectors. This work provides a practical and scalable plasmonic optoelectronic device architecture with real world mid-infrared applications.

physics.optics↗

arXiv2020

Enhanced Room Temperature Infrared LEDs using Monolithically Integrated Plasmonic Materials

Remarkable systems have been reported recently using the polylithic integration of semiconductor optoelectronic devices and plasmonic materials exhibiting epsilon-near-zero (ENZ) and negative permittivity. In traditional noble metals, the ENZ and plasmonic response is achieved near their plasma frequencies, limiting plasmonic optoelectronic device design flexibility. Here, we leverage an all-epitaxial approach to monolithically and seamlessly integrate designer plasmonic materials into a quantum dot light emitting diode (LED), leading to a ~5.6 x enhancement over an otherwise identical non-plasmonic control sample. Devices exhibited optical powers comparable, and temperature performance far superior, to commercially-available devices.

physics.app-ph↗