A5006721562- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- Acoustic Wave Resonator Technologies
- ZnO doping and properties
- Semiconductor materials and devices
- Semiconductor Quantum Structures and Devices
- Metal and Thin Film Mechanics
- Gas Sensing Nanomaterials and Sensors
- Thermal properties of materials
- Ultrasonics and Acoustic Wave Propagation
Leibniz Institute for Crystal Growth
2018-2022
Poznań University of Technology
2018
TU Bergakademie Freiberg
2018
A high seed temperature (2251 °C) reveals the highest deep UV transparency (<italic>α</italic><sub>265nm</sub> = 27 cm<sup>−1</sup>), a structural perfection (EPD 9 × 10<sup>3</sup> cm<sup>−2</sup>) and suitable growth rate (<italic>R</italic> 200 μm h<sup>−1</sup>).
Abstract Carbon‐doping of GaN layers with thickness in the mm‐range is performed by hydride vapor phase epitaxy. Characterization optical and electrical measurements reveals semi‐insulating behavior a maximum specific resistivity 2 × 10 Ω cm at room temperature found for carbon concentration 8.8 18 −3 . For higher levels up to 3.5 19 , slight increase conductivity observed related self‐compensation passivation acceptor. The acceptor can be identified as C N an activation energy 0.94 eV...
Carbon doped GaN crystals grown by hydride vapor phase epitaxy have been investigated using mid-infrared and near-ultraviolet absorption spectroscopy. Two local vibrational modes (LVMs) at 1679 cm−1 1718 as well an shoulder in front of the band edge are discovered, all which increase intensity with carbon concentration. The LVMs similar wavenumber position to LVM formerly observed carbon-rich AlN unambiguously assigned a tri-carbon defect. Together polarization dependence LVMs, we conclude...
Carbon doping is used to obtain semi-insulating GaN crystals. If the carbon concentration exceeds 5 × 1017 cm−3, atoms increasingly form triatomic clusters. The tri-carbon defect structure unambiguously proven by isotope effect on defects' local vibrational modes (LVMs) originally found in samples containing of natural isotopic composition (∼99% 12C, ∼1% 13C) at 1679 cm−1 and 1718 cm−1. Number, spectral positions, intensities LVMs for enriched with 13C ∼50%) are consistently interpreted...
Carbon doped GaN grown by hydride vapor phase epitaxy was investigated photoluminescence and excitation spectroscopy covering a broad range of carbon concentrations. Above bandgap reveals typical transitions related to CN CN−Hi that decrease with increasing concentration. Besides the formation nonradiative defects, complexes containing more than one atom is proposed be responsible for this reduction. Below an intense emission band around 1.62 eV [C] &gt;1018cm−3 shown most efficiently...
Bulk single-crystalline aluminum nitride (AlN) is potentially a key component for low-loss high-temperature piezoelectric devices. However, the incorporation of electrically active impurities and defects during growth AlN may adversely affect performance resonators especially at high temperatures. The electrical conductivity electromechanical losses in bulk single crystals are analyzed temperature range 300–1200 K with respect to various contents growth-related them. For [O]/[C] ≤ 1, an...
AlN bulk single crystals grown by the physical vapor transport method may be beneficially applied as substrates for deep ultraviolet light emitting devices or a basic material piezoelectric resonators operating at high temperatures. Identification of point defects which deteriorate optical, electrical, and electromechanical properties such applications is subject present work. Using Raman spectroscopy, two local vibrational modes (LVMs) were discovered wave numbers 1189 cm−1 1148 cm−1. By...
In this work, we study the absorption properties of AlN in range 1.5–5.5 eV, as well metastable change induced by ultraviolet (UV) irradiation (photochromism). We also restoration initial state under action 2–4 eV or elevated temperatures. UV results a decrease coefficient from 110 to 55 cm−1 at 4.7 while visible range, increases values below 5 ∼35 cm−1. Measurements with two linear polarizations, E ∥ c and ⊥ c, provide determination several different bands 2.6, 2.8, 3.4, 4.0, 4.5, 4.8 eV....
A bulk photovoltaic effect was observed in insulating carbon-doped gallium nitride crystals by investigating the light-induced change of contact potential difference with a Kelvin probe as function carbon concentration crystal. Bulk polarization caused excitation defects setting at photon energies 0.95--1.05 eV (C1) and 2.5--2.6 (C3). From dependence on concentration, C1 can be assigned to isolated C3 tricarbon defects.
This work examines the carbon defects associated with recently reported and novel peaks of infrared (IR) absorption Raman scattering appearing in GaN crystals at ($^{12}C$) doping range concentrations from $3.2*10^{17}$ to $3.5*10^{19} cm^{-3}$. 14 unique vibrational modes are observed samples grown by hydride vapor phase epitaxy (HVPE) then compared defect properties predicted first-principles calculations. The frequency shift two $^{13}C$ enriched related effect isotope mass indicates six...