Jay M. Shah

Bio: Jay M. Shah is an academic researcher. The author has contributed to research in topics: Ohmic contact & p–n junction. The author has an hindex of 1, co-authored 1 publications receiving 440 citations.

Experimental analysis and theoretical model for anomalously high ideality factors (n≫2.0) in AlGaN/GaN p-n junction diodes

Abstract: Diode ideality factors much higher than the expected values of 1.0 to 2.0 have been reported in GaN-based p-n junctions. It is shown that moderately doped unipolar heterojunctions as well as metal-semiconductor junctions, in particular the metal contact to p-type GaN, can increase the ideality factor to values greater than 2.0. A relation is derived for the effective ideality factor by taking into account all junctions of the diode structure. Diodes fabricated from a bulk GaN p-n junction and a p-n junction structure with a p-type AlGaN/GaN superlattice display ideality factors of 6.9 and 4.0, respectively. These results are consistent with the theoretical model and the fact that p-type AlGaN/GaN superlattices facilitate the formation of low-resistance ohmic contacts.

Coaxial Group III−Nitride Nanowire Photovoltaics

Abstract: Coaxial core/shell nanowires represent an important class of nanoscale building blocks with substantial potential for exploring new concepts and materials for solar energy conversion. Here, we report the first experimental realization of coaxial group III−nitride nanowire photovoltaic (PV) devices, n-GaN/i-InxGa1−xN/p-GaN, where variation of indium mole fraction is used to control the active layer band gap and hence light absorption. Current−voltage data reveal clear diode characteristics with ideality factors from 3.9 to 5.6. Electroluminescence measurements demonstrate tunable emission from 556 to 371 nm and thus confirm band gap variations in the InxGa1−xN active layer from 2.25 to 3.34 eV as In composition is varied. Simulated one-sun AM 1.5G illumination yielded open-circuit voltages (Voc) from 1.0 to 2.0 V and short-circuit current densities (Jsc) from 0.39 to 0.059 mA/cm2 as In composition is decreased from 0.27 to 0 and a maximum efficiency of ∼0.19%. The n-GaN/i-InxGa1−xN/p-GaN nanowire devices a...

Near-Infrared Photodetector Based on MoS2/Black Phosphorus Heterojunction

Abstract: Two-dimensional (2D) materials present their excellent properties in electronic and optoelectronic applications, including in ultrafast carrier dynamics, layer-dependent energy bandgap, tunable optical properties, low power dissipation, high mobility, transparency, flexibility, and the ability to confine electromagnetic energy to extremely small volumes. Herein, we demonstrate a photodetector with visible to near-infrared detection range, based on the heterojunction fabricated by van der Waals assembly between few-layer black phosphorus (BP) and few-layer molybdenum disulfide (MoS2). The heterojunction with electrical characteristics which can be electrically tuned by a gate voltage achieves a wide range of current-rectifying behavior with a forward-to-reverse bias current ratio exceeding 103. The photoresponsivity (R) of the photodetector is about 22.3 A W–1 measured at λ = 532 nm and 153.4 mA W–1 at λ = 1.55 μm with a microsecond response speed (15 μs). In addition, its specific detectivity D* is calcul...

Ultralow-threshold electrically pumped quantum-dot photonic-crystal nanocavity laser

Abstract: Researchers demonstrate continuous-wave lasing from a quantum dot photonic crystal nanocavity at temperatures of up to 150 K. The achieved lasing thresholds of 181 nA (at 50 K) and 287 nA (at 150 K) are record-lows for any type of electrically pumped laser.

Tunable GaTe-MoS2 van der Waals p–n Junctions with Novel Optoelectronic Performance

Abstract: P-n junctions based on vertically stacked van der Waals (vdW) materials have attracted a great deal of attention and may open up unforeseen opportunities in electronics and optoelectronics. However, due to the lack of intrinsic p-type vdW materials, most previous studies generally adopted electrical gating, special electrode contacts, or chemical doping methods to realize p-n vdW junctions. GaTe is an intrinsic p-type vdW material with a relatively high charge density, and it has a direct band gap that is independent of thickness. Here, we report the construction of ultrathin and tunable p-GaTe/n-MoS2 vdW heterostructure with high photovoltaic and photodetecting performance. The rectification ratio, external quantum efficiency, and photoresponsivity are as high as 4 × 105, 61.68%, and 21.83 AW–1, respectively. In particular, the detectivity is up to 8.4 × 1013 Jones, which is even higher than commercial Si, InGaAs photodetectors. This study demonstrates the promising potential of p-GaTe/n-MoS2 heterostruc...