A5104133900- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- ZnO doping and properties
- Semiconductor materials and devices
- Photocathodes and Microchannel Plates
- Metal and Thin Film Mechanics
- Radioactive Decay and Measurement Techniques
- Acoustic Wave Resonator Technologies
- Biosensors and Analytical Detection
- bioluminescence and chemiluminescence research
- Chemical Thermodynamics and Molecular Structure
- Semiconductor Quantum Structures and Devices
- Silicon and Solar Cell Technologies
- Lanthanide and Transition Metal Complexes
- Medical Imaging and Pathology Studies
- Thin-Film Transistor Technologies
- Nuclear Physics and Applications
Technische Universität Berlin
2019-2025
University of Cambridge
2022
Georgia Institute of Technology
2022
Aluminium Gallium Nitride (AlGaN) based light emitting diodes (LED) are the enabling technology for compact emitters of deep ultraviolet (DUV) radiation and in high demand environmental medical applications. The efficiency recent DUV LEDs is range a few percent providing some potential improvement. Apart from extraction hole injection into active region presents major obstacle towards more efficient LEDs. In this work, we investigate emission spectra mixed multi quantum well (MQW) LED to...
Abstract The effect of the quantum well number (n QW ) in far ultraviolet-C light emitting diodes (far-UVC LEDs) on optical power, external efficiency (EQE) and degradation has been investigated. AlGaN-based multi-quantum (MQW) LEDs designed for emission at 233 nm 226 with nQW between 1 30 are compared. A positive correlation power 200 mA L70 lifetime large n was observed. For numbers 6 ≤ 15 result powers 4 – 5 mW (corresponding to a maximum EQE 0.47 % = 15) lifetimes 9 13 h. For
n...
<title>Abstract</title> AlGaN alloys with high Al content offer the possibility to create deep ultraviolet (UV) light sources emitting at wavelengths ≤ 240 nm enhanced quantum efficiency. However, pushing limits of band gap energies towards higher values leads problems n-type doping standard choice Si donors when surpasses ∼80 %. This is due formation so-called negative DX center where Si-N bond ruptured, followed by a displacement N atom. In this paper, we show that amphoteric nature dopant...
We propose a detailed approach for modeling the C-V characteristic of complex heterostructure-based devices, investigating case UV-C LEDs. The study is based on combined experimental measurements and TCAD simulations, explores: i) impact defects at critical interfaces apparent charge profile; ii) dependence efficiency carrier injection toward QWs; iii) non-ideal partially-rectifying p-contact curves. By accounting these processes non-idealities, we were able to achieve good reproduction...
In this work, the growth and conductivity of semipolar AlxGa1−xN:Si with (11-22) orientation are investigated. (x = 0.60 ± 0.03 x 0.80 0.02) layers were grown different SiH4 partial pressures, electrical properties determined using Hall measurements at room temperature. The aluminum mole fraction was measured by wavelength dispersive x-ray spectroscopy diffraction, Si-concentration secondary ion mass spectroscopy. Layer resistivities as low 0.024 Ω cm for 0.6 0.042 0.8 achieved. For both...
We investigated the effect of treating surface n-Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.87</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">0.13</sub> N:Si by O xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> or SF xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> plasma on properties subsequently deposited and annealed V/Al/Ni/Au contacts. Whereas an treatment increases contact resistivity, decreases it. The operating...
During the epitaxy of AlGaN on sapphire for deep UV emitters, significant lattice mismatch leads to highly strained heterojunctions and formation threading dislocations. Combining cathodoluminescence, electron beam induced current x-ray microanalysis reveal that dislocations with a screw component permeate through state-of-the-art UVC LED heterostructure into active region perturb their local environment in each layer as growth progresses. In addition acting non-radiative recombination...
The effect of the active region growth temperature ( T MQW ) on external quantum efficiency (EQE) AlGaN‐based far‐ultraviolet‐C light‐emitting diodes (far‐UVC LEDs) emitting near 235 nm is investigated. AlGaN multi‐quantum well (MQW) regions are grown at temperatures between 850 and 1100 °C by metal‐organic vapor‐phase epitaxy, while special care taken to keep aluminum mole fractions thicknesses constant for all MQWs. Temperature‐ excitation‐power‐dependent photoluminescence spectroscopy...
The hole transport and the carrier distribution in AlGaN-based far-ultraviolett (UVC) light emitting diodes (LEDs) around 233 nm was investigated. Temperature-dependent electroluminescence measurements on dual wavelength AlGaN multiple quantum well (MQW) LEDs show a strong shift spectral power from 250 to with decreasing temperature. Comparing experimental data simulation shows that mobility electron ratios have significant influence injection efficiency (CIE) change is originating MQWs....
The effect of bulk AlN single‐crystal substrate thickness on the light extraction efficiency and external quantum far ultraviolet‐C emitting diodes (far‐UVC LEDs) has been investigated. AlGaN multi‐quantum well LEDs designed for emission around 235 nm are grown by metal organic vapor phase epitaxy low defect density substrates as AlN/sapphire templates. As is thinned step‐by‐step from 550 to 70 μm chemo‐mechanical polishing, output power increased 3 μW a 110 (on‐wafer at dc current 100 mA)....
Electrical and optical excitation of the active region a UVB LED chip was combined while imaging its in-plane lateral light emission by UV camera. This made it possible to distinguish between spatial distribution in current density efficiency radiative recombination charge carriers. It is demonstrated that degradation more prominent areas where local increased throughout long-term operation. will be shown how intensity distributions UVC LEDs are affected operation current, design, mesa edges.
Due to changes in the spontaneous and piezoelectric polarization, AlGaN/GaN heterostructures exhibit strong polarization fields at heterointerfaces. For quantum wells, lead a band bending redshift of emission wavelength, known as quantum-confined Stark effect. In this paper thin AlGaN layers GaN matrix were determined by evaluating depletion region width comparison reference sample without heterostructure using capacitance–voltage-measurements. The for Al0.09Ga0.91N (0.6 ± 0.7 MV cm−1),...
Far-UVC LEDs are interesting for applications such as skin-tolerant inactivation of multiresistant pathogens and gas sensing. We present the development 233 nm AlGaN-based far-UVC with an emission power 3 mW at 200 mA L50 lifetime more than 1000 h, after burn-in. Additionally, design a LED-based irradiation system, spectral filter which supresses >240 nm, to study bacteria skin compatibility radiation will be presented. The system can used homogeneously irradiate target area 70 mm diameter...