Photodetectors with GeSn nanocrystals in Si3N4 matrix highly photosensitive from 0.5 µm to 2.4 µm (GeSnPhotoSiNdet)

Project Director: Dr. Ionel STAVARACHE
Contract ID: cod PN-III-P1-1.1-TE-2021-1491
Project Director: Dr. Ionel Stavarache
Project Type: National
Project Program: Program 1 - Development of the national CD system;
Funded by: Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii - UEFISCDI
Contractor: National Institute of Materials Physics (NIMP)
Contract no.: TE 71 / 2022
Status: In progress
Data de inceput: May 15st, 2022
Data finalizarii: May 14st, 2024
The project goal is to fabricate a demonstrator for photodetector device with GeSn-nps (top contact/GeSn-nps:Si3N4/Si and/or quartz substrate/bottom contact), having targeted parameters: photocurrent to dark current ratio at least 2 orders of magnitude, fast photoresponse time:μs, spectral window extended toward 2.4 µm, high responsivity and good detectivity characteristics. We propose a new and original approach, by using an active layer that give an extended spectral limit in SWIR due to Si3N4 properties to induce a tensile strain in film. This consists in co-deposition or multilayer of different GeSn compozition and content in Si3N4. Objectives: O1: Fabrication by MS of the structure, GeSn-nps:Si3N4/ Si or quartz substrate, by using different novel approaches. For this, the critical deposition parameters (target power, work pressure, gas flux or substrate temperature) will be finely tuned to be optimized. O2: Formation of the GeSn-nps in Si3N4 matrix with controlled morphology (size, uniformity and density); O3: Developing the test samples with photoconductive properties controlled by morphology, completely characterized; O4: Obtaining the demonstrator of the photodetector device having targeted parameters, functionally tested according to TRL 3. Dissemination of the results: 1 patent, 3 ISI-quoted journals, 2 contributions to conferences and web page.

Dr. Ionel Stavarache

Dr. Ana-Maria Lepadatu

Dr. Catalin Palade

Dr. Ioana-Maria Avram Dascalescu

Dr. Adrian Slav

Drd. Mihalcea Catalina-Gabriela

Dr. Catalin Negrila

Drd. Ovidiu Cojocaru

Stage I/2022

In the Stage I/2022, photodetector structures based on GeSnSi3N4 films in which the Sn concentration in the film was varied between ~4%vol. and ~ 18 %vol. were made. The films were deposited by magnetron sputtering on Si and quartz substrate maintained at room temperature during deposition.

The formation of GeSn nanocrystals/dots in GeSnSi3N4 films was achieved by thermal annealing RTA, after optimizing the necessary parameters, namely temperatures in the range of 325 - 700 °C.

The morphology and structure of the investigated films are strongly dependent on the Sn concentration in the GeSnSi3N4 films. In the amorphous films with increased Sn concentration, the structure is more dilated in the sense that the distance between the atoms in the first coordination sphere and the second coordination sphere is increased. This phenomenon also occurs in crystallized GeSn, i.e. the lattice constant increases with the increase in Sn concentration.

Optical investigations highlight the influence of the Sn concentration in the films on the absorption threshold. In the films where the Sn concentration is approximately 18 %vol, the absorption threshold has a value of 0.5 eV compared to the value of 0.7 eV corresponding to a Sn concentration of ~4 %vol.

The I – V characteristics obtained on GeSnSi3N4 / Si films show that the photocurrent is 4 orders of magnitude higher than the dark current and is strongly dependent on the measurement temperature. In addition, the spectral dependence of the photocurrent on these films presents a wide sensitivity band, in the range 520 - 1750 nm. The obtained results from the optical investigations are in agreement with the spectral ones and demonstrate that these films have adequate photoconductive properties for the manufacture of photodetectors.

In conclusion, the objectives and activities proposed for Stage I/2022 were fully achieved.



Lucrare indexata ISI:

“Extended near infrared photo-response influenced by host matrix change in Ge nanoparticle-based films”, I. Stavarache, C. Palade, A. Slav, P. Prepelita, V. S. Teodorescu, M. L. Ciurea, IEEE conference, 45th Edition of International Semiconductor Conference (CAS), pp. 231-234, 2022 October 12-14, Sinaia, Romania; IEEE Catalog Number: CFP22CAS-USB;
ISBN: 978-1-6654-5253-3


Ph.D. Ionel Stavarache

National Institute of Materials Physics,

405A Atomistilor Street, Magurele, Ilfov, PO BOX MG-7, 077125




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