Institute of High Pressure Physics

Dear Ladies and Gentlemen,

We are pleased to invite you to the IHPP PAS Seminar on Nitride Semiconductors. The next presentation will be held in a hybrid mode – at the New Technologies seminar room, Al. Prymasa Tysiąclecia 98, and through Zoom platform (to get the link, please contact us at nitride_seminar@mail.unipress.waw.pl ).

The next seminar is scheduled on Monday 29.05.2023 at 13:00.

Speaker: dr inż. Joanna Moneta (IHPP PAS, NL-12)

Title: Peculiarities of the strain relaxation in InGaN layers

Abstract:

The idea of using relaxed InGaN layers as pseudo-substrates for the growth of InGaN-based devices has emerged in the last years. While most of approaches of gaining relaxed InGaN are based on the elastically relaxed layers obtained by preparation of compliant layer (e.g., porous GaN) and subsequent patterning, in our attempt we focus on InGaN layers relaxed plastically by the introduction of misfit dislocations. An understanding of the dislocation formation process which allows prediction and control of the properties of relaxed InGaN layers is essential for achieving good quality InGaN/GaN templates.
InGaN layers with indium content close to 20% deposited on various types of (0001)-GaN substrates were studied. The growth was carried out by either Molecular Beam Epitaxy (MBE) or Metalorganic Vapor Phase Epitaxy (MOVPE). Structural analysis was done by means of transmission electron microscopy, cathodoluminescence imaging, traditional X-ray diffractometry and full-field X-ray diffraction microscopy.
The seminar will discuss the mechanisms of misfit dislocations nucleation and glide and the influence of GaN-substrate misorientation on the strain relaxation process. The impact on the structural properties of InGaN/GaN templates will be addressed.

Sincerely,

Tadeusz Suski
Piotr Perlin
Anna Kafar

Vertical GaN power devices are promising candidates for future kV-class power electronics due to the wide bandgap and high critical electric field (EC) of GaN. Vertical architectures provide the possibility of downsizing the devices and increasing their reliability. However, still a few challenges have to be addressed such as selective area doping, Schottky contact formation and drift layer growth.

In the next Thursday UNIPRESS seminar, Kacper Sierakowski from our Institute, the Crystal Growth Laboratory, will present the current state of the art in ion implantation in GaN and summarize the recent progress in the design of Junction Barrier Schottky (JBS) diodes.

The Seminar “Magnesium ion implantation – key technology for GaN power electronics” will be held on Thursday, May 25, 2023 at 15:00 on Zoom platform. To get the link to join the seminar, please contact us at dyrekcja@unipress.waw.pl

Dear Ladies and Gentlemen,

We are pleased to invite you to the IHPP PAS Seminar on Nitride Semiconductors. The next presentation will be held in a hybrid mode – at the New Technologies seminar room, Al. Prymasa Tysiąclecia 98, and through Zoom platform (to get the link, please contact us at nitride_seminar@mail.unipress.waw.pl ).

The next seminar is scheduled on Monday 22.05.2023 at 14:00.

Speaker: prof. dr hab. Piotr Kossacki (University of Warsaw, Institute of Experimental Physics)

Title: Ultrafast dynamics of excitons in monolayers of semiconductor TMDs

Abstract:
Monolayers of transition metal dichalcogenides (TMDs) draw a lot of attention as semiconducting materials with robust optical properties, strong Coulomb interaction and an optically accessible valley degree of freedom. Extraordinary properties of exciton complexes lead to new possibilities of exploration of nonlinear effects.
In my seminar, I will focus on ultrafast studies of exciton dynamics explored by time resolved photoluminescence, FWM and femtosecond pump-probe experiments. The studies of neutral and charged exciton optical response show strong interactions between different complexes. For example creation of CX population in a given K,K’ valley leads to the capture of available free carriers in the opposite valley and reduces the interaction of neutral X with the Fermi sea. From the valley-resolved analysis of the observed effects we are also able to extract the spin-valley relaxation times of free carriers as a function of carrier density. The several effects related to interaction with carries such as the oscillator strength variation and energy shift will be discussed and compared to the cases of ordinary quantum wells. I will point similarities and differences in the complex landscape of exciton-exciton and exciton-carrier interactions in both two dimensional systems.

Sincerely,

Tadeusz Suski
Piotr Perlin
Anna Kafar

Dear Ladies and Gentlemen,

We are pleased to invite you to the IHPP PAS Seminar on Nitride Semiconductors. The next presentation will be held in a hybrid mode – at the New Technologies seminar room, Al. Prymasa Tysiąclecia 98, and through Zoom platform (to get the link, please contact us at nitride_seminar@mail.unipress.waw.pl ).

The next seminar is scheduled on Monday 08.05.2023 at 14:00.

Speaker: prof. Michał Leszczyński (IHPP PAS, NL-12)

Title: Point defects in nitride semiconductors - do they really exist?

Presence of vacancies enables atoms to move. In the seminar, the following examples of experimental data will be given: i) diffusion of indium atoms in InGaN quantum wells that leads to well homogenization and decomposition, ii) diffusion of Al atoms smearing out the AlGaN/GaN interfaces, iii) diffusion of silicon and magnesium dopants. These data were obtained during annealing with and without gallium atoms in the gas above the samples, what had a significant influence on the diffusion.

Sincerely,

Tadeusz Suski
Piotr Perlin
Anna Kafar