TY  - JOUR
AU  - Pohorelec, O.
AU  - Ťapajna, M.
AU  - Gregušová, D.
AU  - Gucmann, F.
AU  - Hasenöhrl, S.
AU  - Haščík, Š.
AU  - Stoklas, R.
AU  - Seifertová, A.
AU  - Pécz, Béla
AU  - Tóth, Lajos
AU  - Kuzmík, J.
TI  - Investigation of interfaces and threshold voltage instabilities in normally-off MOS-gated InGaN/AlGaN/GaN HEMTs
JF  - APPLIED SURFACE SCIENCE
J2  - APPL SURF SCI
VL  - 528
PY  - 2020
PG  - 6
SN  - 0169-4332
DO  - 10.1016/j.apsusc.2020.146824
UR  - https://m2.mtmt.hu/api/publication/31354912
ID  - 31354912
AB  - Polarization engineering is a promising approach to achieve high positive threshold voltage (Vth) in GaN-based metal-oxide-semiconductor high electron mobility transistors (MOS HEMTs). In this paper, we investigate all critical interfaces of polarization-engineered normally-off Al2O3/InGaN/AlGaN/GaN MOS HEMTs using transmission electron microscopy and X-ray photoelectron spectroscopy. Mechanisms of threshold voltage (VTH) instabilities are also analyzed. Devices were subjected to positive-bias stress-recovery experiments to capture the transient change in Vth. We propose a model that explains observed peculiar behavior and discuss the role of 2-dimensional hole gas (2DHG) in Al2O3/InGaN/AlGaN/GaN MOS HEMTs Vth shift.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Ballabio, Andrea
AU  - Bietti, Sergio
AU  - Scaccabarozzi, Andrea
AU  - Esposito, Luca
AU  - Vichi, Stefano
AU  - Fedorov, Alexey
AU  - Vinattieri, Anna
AU  - Mannucci, Cosimo
AU  - Biccari, Francesco
AU  - Nemcsics, Ákos
AU  - Tóth, Lajos
AU  - Miglio, Leo
AU  - Gurioli, Massimo
AU  - Isella, Giovanni
AU  - Sanguinetti, Stefano
TI  - GaAs epilayers grown on patterned (001) silicon substrates via suspended Ge layers
JF  - SCIENTIFIC REPORTS
J2  - SCI REP
VL  - 9
PY  - 2019
IS  - 1
PG  - 8
SN  - 2045-2322
DO  - 10.1038/s41598-019-53949-x
UR  - https://m2.mtmt.hu/api/publication/30936719
ID  - 30936719
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Gregušová, Dagmar
AU  - Tóth, Lajos
AU  - Pohorelec, Ondrej
AU  - Hasenöhrl, Stanislav
AU  - Haščík, Štefan
AU  - Cora, Ildikó
AU  - Fogarassy, Zsolt
AU  - Stoklas, Roman
AU  - Seifertová, Alena
AU  - Blaho, Michal
AU  - Laurenčíková, Agáta
AU  - Oyobiki, Tatsuya
AU  - Pécz, Béla
AU  - Hashizume, Tamotsu
AU  - Kuzmík, Ján
TI  - InGaN/(GaN)/AlGaN/GaN normally-off metal-oxide-semiconductor high-electron mobility transistors with etched access region
JF  - JAPANESE JOURNAL OF APPLIED PHYSICS (2008)
J2  - JPN J APPL PHYS
VL  - 58
PY  - 2019
IS  - C
PG  - 6
SN  - 0021-4922
DO  - 10.7567/1347-4065/ab06b8
UR  - https://m2.mtmt.hu/api/publication/30682160
ID  - 30682160
AB  - The proposal and processing aspects of the prove-of-concept InGaN/GaN/AlGaN/GaN metal-oxide-semiconductor (MOS) high-electron mobility transistor with etched access regions are addressed. Full strain and decent quality of the epitaxial system comprising 4 nm In0.16Ga0.84N/3 nm GaN/5 nm Al0.27Ga0.73N are observed using a high-resolution transmission-electron microscopy and by deformation profile extractions. Large negative polarization charge in the MOS gate stack provides the HEMT normally-off operation, while free electrons are populated at access regions after etching. Consecutive passivation by 10 nm Al2O3 together with annealing at 300 °C improved the Al2O3/semiconductor interface, with the threshold voltage (V T ) reaching 1 V. Improvements of the present concept in comparison to the previous one with a gate recess were proved by showing the decreased drain leakage current and increased breakdown voltage.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Heuken, L
AU  - Alshahed, M
AU  - Ottaviani, A
AU  - Alomari, M
AU  - Heuken, M
AU  - Wächter, C
AU  - Bergunde, T
AU  - Cora, Ildikó
AU  - Tóth, Lajos
AU  - Pécz, Béla
AU  - Burghartz, JN
TI  - Temperature Dependent Vertical Conduction of GaN HEMT Structures on Silicon and Bulk GaN Substrates
JF  - PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
J2  - PHYS STATUS SOLIDI A-APPL MAT SCI
VL  - 216
PY  - 2019
IS  - 1
PG  - 7
SN  - 1862-6300
DO  - 10.1002/pssa.201800482
UR  - https://m2.mtmt.hu/api/publication/27700291
ID  - 27700291
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Szenes, György
AU  - Tóth, Lajos
TI  - Basic restrictions for theories of ion-induced track formation: ignored relationships between experimental data
JF  - PHYSICA SCRIPTA
J2  - PHYS SCR
VL  - 94
PY  - 2019
IS  - 11
PG  - 9
SN  - 0031-8949
DO  - 10.1088/1402-4896/ab300c
UR  - https://m2.mtmt.hu/api/publication/30739221
ID  - 30739221
AB  - Ion-induced track data are analyzed without the application of any model for revealing the existing relationships between them. Published data are completed with some new ones. Prethinned Y3Fe5O12 samples were irradiated by C60 ions with 3.5, 5 and 7 MeV energy. Track radii Re were measured by electron microscopy. It was derived from the data that the electronic (Se) and nuclear stopping (Sn) powers are combined as αSe+βSn when they have a simultaneous effect. α=0.45 was derived from experiments on Y3Fe5O12. When using larger database α varies in the range 0.4>α>0.17 with increasing ion energy that is valid for monoatomic irradiations as well, and this is the origin of the reduction of Re with the increasing ion energy in insulators. A Gaussian relationship exists between melting temperatures Tm and track radii in track forming insulators for Se/N=constant (N – atomic number density). Due to this Tm is the unique controlling materials parameter for the track size. Consequences for the parameters of the induced temperature distributions are discussed. The conclusions were deduced directly from the raw experimental data, therefore, the derived relationships should be followed by any theoretical model.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Alshahed, M
AU  - Heuken, L
AU  - Alomari, M
AU  - Cora, Ildikó
AU  - Tóth, Lajos
AU  - Pécz, Béla
AU  - Wachter, C
AU  - Bergunde, T
AU  - Burghartz, JN
TI  - Low-Dispersion, High-voltage, Low-Leakage GaN HEMTs on Native GaN Substrates
JF  - IEEE TRANSACTIONS ON ELECTRON DEVICES
J2  - IEEE T ELECTRON DEV
VL  - 65
PY  - 2018
IS  - 7
SP  - 2939
EP  - 2947
PG  - 9
SN  - 0018-9383
DO  - 10.1109/TED.2018.2832250
UR  - https://m2.mtmt.hu/api/publication/3401186
ID  - 3401186
AB  - In this paper, the advantages of GaN high electron mobility transistors (HEMTs) grown on native GaN over GaN/Si or GaN/sapphire substrates are investigated and correlated with epitaxial material quality. Transmission electron microscopy plan-view and cross-sectional analyses of GaN/GaN reveal dislocation densities below 1 x 10(6) cm(-2), which is at least three orders of magnitude lower than that of GaN/Si or GaN/sapphire. In the case of GaN/Si, the dislocations not only originate from the substrate/nucleation layer interface, but also the strain relief and isolation buffer stacks are main contributors to the dislocation density. GaN/GaN HEMTs show superior electrical and thermal performance and feature three orders of magnitude lower OFF-state leakage. The current collapse (also referred to as current dispersion or R-ON-increase) after stress bias is less than 15% compared with 50% in the case of GaN/Si. A 2% drop of the ON-state current due to self-heating in dc operation when compared with 13% and 16% for GaN/Si and GaN/sapphire, respectively. The GaN/Si thermal performance becomes comparable to that of GaN/GaN only after substrate removal. Therefore, GaN/GaN provides high ON-state current, low OFF-state leakage current, minimal current collapse, and enhanced thermal power dissipation capability at the same time, which can directly be correlated with the absence of high dislocation density.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Bietti, S
AU  - Basset, FB
AU  - Scarpellini, D
AU  - Fedorov, A
AU  - Ballabio, A
AU  - Esposito, L
AU  - Elborg, M
AU  - Kuroda, T
AU  - Nemcsics, Ákos
AU  - Tóth, Lajos
AU  - Manzoni, C
AU  - Vozzi, C
AU  - Sanguinetti, S
TI  - Ga metal nanoparticle-GaAs quantum molecule complexes for terahertz generation
JF  - NANOTECHNOLOGY
J2  - NANOTECHNOLOGY
VL  - 29
PY  - 2018
IS  - 36
PG  - 8
SN  - 0957-4484
DO  - 10.1088/1361-6528/aacd20
UR  - https://m2.mtmt.hu/api/publication/3400962
ID  - 3400962
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Nemcsics, Ákos
AU  - Ürmös, Antal
AU  - Tóth, Lajos
TI  - Droplet Epitaxy and its Possibilities in Nano-electronics
JF  - International Symposium on Next-Generation Electronics
J2  - International Symposium on Next-Generation Electronics
VL  - 2018
PY  - 2018
SP  - 122
EP  - 124
PG  - 3
SN  - 2378-8593
DO  - 10.1109/ISNE.2018.8394694
UR  - https://m2.mtmt.hu/api/publication/27519782
ID  - 27519782
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Ťapajna, M
AU  - Stoklas, R
AU  - Gregušová, D
AU  - Gucmann, F
AU  - Hušeková, K
AU  - Haščík, Š
AU  - Fröhlich, K
AU  - Tóth, Lajos
AU  - Pécz, Béla
AU  - Brunner, F
AU  - Kuzmík, J
TI  - Investigation of ‘surface donors’ in Al2O3/AlGaN/GaN metal-oxide-semiconductor heterostructures: Correlation of electrical, structural, and chemical properties
JF  - APPLIED SURFACE SCIENCE
J2  - APPL SURF SCI
VL  - 426
PY  - 2017
SP  - 656
EP  - 661
PG  - 6
SN  - 0169-4332
DO  - 10.1016/j.apsusc.2017.07.195
UR  - https://m2.mtmt.hu/api/publication/3254420
ID  - 3254420
AB  - III-N surface polarization compensating charge referred here to as ‘surface donors’ (SD) was analyzed in Al2O3/AlGaN/GaN metal-oxide-semiconductor (MOS) heterojunctions using scaled oxide films grown by metal-organic chemical vapor deposition at 600 °C. We systematically investigated impact of HCl pre-treatment prior to oxide deposition and post-deposition annealing (PDA) at 700 °C. SD density was reduced down to 1.9 × 1013 cm−2 by skipping HCl pre-treatment step as compared to 3.3 × 1013 cm−2 for structures with HCl pre-treatment followed by PDA. The nature and origin of SD was then analyzed based on the correlation between electrical, micro-structural, and chemical properties of the Al2O3/GaN interfaces with different SD density (NSD). From the comparison between distributions of interface traps of MOS heterojunction with different NSD, it is demonstrated that SD cannot be attributed to interface trapped charge. Instead, variation in the integrity of the GaOx interlayer confirmed by X-ray photoelectron spectroscopy is well correlated with NSD, indicating SD may be formed by border traps at the Al2O3/GaOx interface. © 2017 Elsevier B.V.
LA  - English
DB  - MTMT
ER  - 

TY  - JOUR
AU  - Ťapajna, Milan
AU  - Válik, Lukáš
AU  - Gucmann, Filip
AU  - Gregušová, Dagmar
AU  - Fröhlich, Karol
AU  - Haščík, Štefan
AU  - Dobročka, Edmund
AU  - Tóth, Lajos
AU  - Pécz, Béla
AU  - Kuzmík, Ján
TI  - Low-temperature atomic layer deposition-grown Al2O3 gate dielectric for GaN/AlGaN/ GaN MOS HEMTs: Impact of deposition conditions on interface state density
JF  - JOURNAL OF VACUUM SCIENCE AND TECHNOLOGY B-NANOTECHNOLOGY AND MICROELECTRONICS
J2  - J VAC SCI TECHNOL B
VL  - 35
PY  - 2017
IS  - 1
PG  - 8
SN  - 2166-2746
DO  - 10.1116/1.4972870
UR  - https://m2.mtmt.hu/api/publication/3161397
ID  - 3161397
LA  - English
DB  - MTMT
ER  -