Moonhyung Jang - Academia.edu (original) (raw)

Papers by Moonhyung Jang

Research paper thumbnail of Supplementary document for Photoconductive Mechanism of IR Sensitive Iodized PbSe Thin Films via Strong Hole-Phonon Interaction and Minority Carrier Diffusion - 4892666.pdf

Research paper thumbnail of Supplementary document for Laser Annealing to Improve PbSe Thin Films Photosensitivity and Specific Detectivity - 4700258.pdf

Research paper thumbnail of Photoconductive mechanism of IR-sensitive iodized PbSe thin films via strong hole–phonon interaction and minority carrier diffusion

Applied Optics, 2020

Photoconductive PbSe thin films are highly important for mid-infrared imaging applications. Howev... more Photoconductive PbSe thin films are highly important for mid-infrared imaging applications. However, the photoconductive mechanism is not well understood so far. Here we provide additional insight on the photoconductivity mechanism using transmission electron microscopy, x-ray photoelectron microscopy, and electrical characterizations. Polycrystalline PbSe thin films were deposited by a chemical bath deposition method. Potassium iodide (KI) was added during the deposition process to improve the photoresponse. Oxidation and iodization were performed to sensitize the thin films. The temperature-dependence Hall effect results show that a strong hole-phonon interaction occurs in oxidized PbSe with KI. It indicates that about half the holes are trapped by KI-induced self-trapped hole centers (Vk center), which results in increasing dark resistance. The photo Hall effect results show that the hole concentration increases significantly under light exposure in sensitized PbSe, which indicates the photogenerated electrons are compensated by trapped holes. The presence of KI in the PbSe grains was confirmed by I 3d5/2 core-level x-ray photoelectron spectra. The energy dispersive x-ray spectra obtained in the scanning transmission electron microscope show the incorporation of iodine during the iodization process on the top of PbSe grains, which can create an iodine-incorporated PbSe outer shell. The iodine-incorporated PbSe releases electrons to recombine with holes in the PbSe layer so that the resistance of sensitized PbSe is about 800 times higher than that of PbSe without the iodine-incorporated layer. In addition, oxygen found in the outer shell of PbSe can act as an electron trap. Therefore, the photoresponse of sensitized PbSe is from the difference between the high dark resistance (by KI addition and iodine incorporation) and the low resistance after IR exposure due to electron compensation (by electron traps at grain boundary and electron-hole recombination in KI hole traps).

Research paper thumbnail of Laser annealing to improve PbSe thin film photosensitivity and specific detectivity

Applied Optics, 2020

PbSe thin films were deposited on S i O 2 / S i wafers using chemical bath deposition for mid-wav... more PbSe thin films were deposited on S i O 2 / S i wafers using chemical bath deposition for mid-wave infrared (MWIR) detection. To enhance the photosensitivity of PbSe thin films, oxidation, followed by iodization, was performed to create a P b I 2 / P b S e two-layer system for efficient MWIR detection in the spectral range from 3 µm to 5 µm. A near-infrared (IR) laser annealing was performed after sensitization with 1070 nm wavelength at an energy density of 1 J / c m 2 to selectively heat the PbSe thin films. After IR laser annealing, the change in resistance between dark condition and MWIR illumination improved significantly from 19.8% to 22.6%. In addition, the dark resistance increased by 32.5% after IR laser annealing. IR photoluminescence spectra after IR laser annealing shows an increase in the sub-peak intensities from iodine incorporation. The results indicate that more iodine is incorporated into Se sites at the outer regions of PbSe grains. Therefore, more donors (electro...

Research paper thumbnail of A multiscale materials-to-systems modeling of polycrystalline PbSe photodetectors

Journal of Applied Physics, 2019

We present a physics based multiscale materials-to-systems model for polycrystalline P bSe photod... more We present a physics based multiscale materials-to-systems model for polycrystalline P bSe photodetectors that connects fundamental material properties to circuit level performance metrics. From experimentally observed film structures and electrical characterization, we first develop a bandstructure model that explains carrier-type inversion and large carrier lifetimes in sensitized films. The unique bandstructure of the photosensitive film causes separation of generated carriers with holes migrating to the inverted P bSe|P bI 2 interface, while electrons are trapped in the bulk of the film inter-grain regions. These flows together form the 2-current theory of photoconduction that quantitatively captures the I − V relationship in these films. To capture the effect of pixel scaling and trapped carrier blocking, we develop a model for the metallic contacts with the detector films based on the relative workfunction differences. We also develop detailed models for various physical parameters such as mobility, lifetime, quantum efficiency, noise etc. that connect the detector performance metrics such as responsivity R and specific detectivity D * intimately with material properties and operating conditions. A compact Verilog-A based SPICE model is developed which can be directly combined with advanced digital Read Out Integrated Circuit (ROIC) cell designs to simulate and optimize high performance Focal Plane Arrays (FPAs) which form a critical component in the rapidly expanding market of self-driven automotive, IoTs, security, and embedded applications.

Research paper thumbnail of Electrical transport properties of sensitized PbSe thin films for IR imaging sensors

Semiconductor Science and Technology, 2019

Research paper thumbnail of Electronic structure of conducting Al-doped ZnO films as a function of Al doping concentration

Ceramics International, 2015

Transparent conducting Al-doped ZnO films were deposited by atomic layer deposition with various ... more Transparent conducting Al-doped ZnO films were deposited by atomic layer deposition with various of Al doping concentrations. In order to explain the change in resistivity of Al-doped ZnO films depending on Al doping concentration, we investigated the correlations between the conducting property and electronic structure in terms of atomic configuration, the evolution of the conduction band and band gap, and band alignments (conduction band offset between minimum of conduction band and Fermi level, ΔE CB). ZnO film Al-doped at $ 3 at% and deposited at 250 1C showed the lowest resistivity, which resulted in changes in the conduction band of insulating Al 2 O 3 film, and increases in the band gap and conduction band offset (ΔE CB).

Research paper thumbnail of Properties of chemical bath deposited and sensitized PbSe thin films for IR detection

Semiconductor Science and Technology, 2019

Research paper thumbnail of Supplementary document for Photoconductive Mechanism of IR Sensitive Iodized PbSe Thin Films via Strong Hole-Phonon Interaction and Minority Carrier Diffusion - 4892666.pdf

Research paper thumbnail of Supplementary document for Laser Annealing to Improve PbSe Thin Films Photosensitivity and Specific Detectivity - 4700258.pdf

Research paper thumbnail of Photoconductive mechanism of IR-sensitive iodized PbSe thin films via strong hole–phonon interaction and minority carrier diffusion

Applied Optics, 2020

Photoconductive PbSe thin films are highly important for mid-infrared imaging applications. Howev... more Photoconductive PbSe thin films are highly important for mid-infrared imaging applications. However, the photoconductive mechanism is not well understood so far. Here we provide additional insight on the photoconductivity mechanism using transmission electron microscopy, x-ray photoelectron microscopy, and electrical characterizations. Polycrystalline PbSe thin films were deposited by a chemical bath deposition method. Potassium iodide (KI) was added during the deposition process to improve the photoresponse. Oxidation and iodization were performed to sensitize the thin films. The temperature-dependence Hall effect results show that a strong hole-phonon interaction occurs in oxidized PbSe with KI. It indicates that about half the holes are trapped by KI-induced self-trapped hole centers (Vk center), which results in increasing dark resistance. The photo Hall effect results show that the hole concentration increases significantly under light exposure in sensitized PbSe, which indicates the photogenerated electrons are compensated by trapped holes. The presence of KI in the PbSe grains was confirmed by I 3d5/2 core-level x-ray photoelectron spectra. The energy dispersive x-ray spectra obtained in the scanning transmission electron microscope show the incorporation of iodine during the iodization process on the top of PbSe grains, which can create an iodine-incorporated PbSe outer shell. The iodine-incorporated PbSe releases electrons to recombine with holes in the PbSe layer so that the resistance of sensitized PbSe is about 800 times higher than that of PbSe without the iodine-incorporated layer. In addition, oxygen found in the outer shell of PbSe can act as an electron trap. Therefore, the photoresponse of sensitized PbSe is from the difference between the high dark resistance (by KI addition and iodine incorporation) and the low resistance after IR exposure due to electron compensation (by electron traps at grain boundary and electron-hole recombination in KI hole traps).

Research paper thumbnail of Laser annealing to improve PbSe thin film photosensitivity and specific detectivity

Applied Optics, 2020

PbSe thin films were deposited on S i O 2 / S i wafers using chemical bath deposition for mid-wav... more PbSe thin films were deposited on S i O 2 / S i wafers using chemical bath deposition for mid-wave infrared (MWIR) detection. To enhance the photosensitivity of PbSe thin films, oxidation, followed by iodization, was performed to create a P b I 2 / P b S e two-layer system for efficient MWIR detection in the spectral range from 3 µm to 5 µm. A near-infrared (IR) laser annealing was performed after sensitization with 1070 nm wavelength at an energy density of 1 J / c m 2 to selectively heat the PbSe thin films. After IR laser annealing, the change in resistance between dark condition and MWIR illumination improved significantly from 19.8% to 22.6%. In addition, the dark resistance increased by 32.5% after IR laser annealing. IR photoluminescence spectra after IR laser annealing shows an increase in the sub-peak intensities from iodine incorporation. The results indicate that more iodine is incorporated into Se sites at the outer regions of PbSe grains. Therefore, more donors (electro...

Research paper thumbnail of A multiscale materials-to-systems modeling of polycrystalline PbSe photodetectors

Journal of Applied Physics, 2019

We present a physics based multiscale materials-to-systems model for polycrystalline P bSe photod... more We present a physics based multiscale materials-to-systems model for polycrystalline P bSe photodetectors that connects fundamental material properties to circuit level performance metrics. From experimentally observed film structures and electrical characterization, we first develop a bandstructure model that explains carrier-type inversion and large carrier lifetimes in sensitized films. The unique bandstructure of the photosensitive film causes separation of generated carriers with holes migrating to the inverted P bSe|P bI 2 interface, while electrons are trapped in the bulk of the film inter-grain regions. These flows together form the 2-current theory of photoconduction that quantitatively captures the I − V relationship in these films. To capture the effect of pixel scaling and trapped carrier blocking, we develop a model for the metallic contacts with the detector films based on the relative workfunction differences. We also develop detailed models for various physical parameters such as mobility, lifetime, quantum efficiency, noise etc. that connect the detector performance metrics such as responsivity R and specific detectivity D * intimately with material properties and operating conditions. A compact Verilog-A based SPICE model is developed which can be directly combined with advanced digital Read Out Integrated Circuit (ROIC) cell designs to simulate and optimize high performance Focal Plane Arrays (FPAs) which form a critical component in the rapidly expanding market of self-driven automotive, IoTs, security, and embedded applications.

Research paper thumbnail of Electrical transport properties of sensitized PbSe thin films for IR imaging sensors

Semiconductor Science and Technology, 2019

Research paper thumbnail of Electronic structure of conducting Al-doped ZnO films as a function of Al doping concentration

Ceramics International, 2015

Transparent conducting Al-doped ZnO films were deposited by atomic layer deposition with various ... more Transparent conducting Al-doped ZnO films were deposited by atomic layer deposition with various of Al doping concentrations. In order to explain the change in resistivity of Al-doped ZnO films depending on Al doping concentration, we investigated the correlations between the conducting property and electronic structure in terms of atomic configuration, the evolution of the conduction band and band gap, and band alignments (conduction band offset between minimum of conduction band and Fermi level, ΔE CB). ZnO film Al-doped at $ 3 at% and deposited at 250 1C showed the lowest resistivity, which resulted in changes in the conduction band of insulating Al 2 O 3 film, and increases in the band gap and conduction band offset (ΔE CB).

Research paper thumbnail of Properties of chemical bath deposited and sensitized PbSe thin films for IR detection

Semiconductor Science and Technology, 2019