Institute of High Pressure Physics

Nitride based materials still suffer from the lack of the understanding of the mechanisms of defects formation and their impact on the material properties. Dr Piotr Kruszewski with his collaborators from NL12 laboratory recently used deep-level transient spectroscopy (DLTS) to study Al_xGa_1-xN (x<0.05) grown by MOVPE.

It was shown that the electron emission signal related to the Fe_Ga (0/-) acceptor level splits into individual components due to aluminum fluctuations in the second-nearest neighbor (2NN) shell around the Fe_Ga impurity atoms. The calculations of the probability of finding a given number of aluminum atoms in the 2NN shell of the Fe_Ga defect agreed well with the experimental concentrations determined from Laplace DLTS peak intensities. This finding shows that in dilute Al_xGa_1-xN layers grown by MOVPE, aluminum and iron atoms are randomly distributed in the material. Finally, it was demonstrated that the energy level of the Fe_Ga acceptor with no Al atoms in the 2NN shell in the Al_xGa_1-xN samples shifts linearly with the aluminum content.

The publication "Alloy splitting of the Fe_Ga acceptor level in dilute Al_xGa_1−xN" (P. Kruszewski et al., Appl. Phys. Lett. 123, 222105 (2023)) is the result of the collaboration with colleagues from the Photon Science Institute and Department of Electrical and Electronic Engineering, the University of Manchester cooperating in NCN-OPUS project lead by Dr. Piotr Kruszewski.

Fig.1. Three-dimensional diagram of the Al_xGa_1-xN alloy showing two shells of atoms surrounding the Fe_Ga impurity (top image) and Laplace DLTS spectra for the Fe_Ga acceptor state in Al_xGa_1-xN (x ≤ 0.05) samples with energy-level-difference values at X axis (bottom image).

We are happy to share that dr inż. Tomasz Sochacki and dr inż. Marta Sawicka are the laureates of a LIDER Program funded by National Center for Research and Development (NCBiR).

• The project "Innovative technology for fabricating semi-insulating gallium nitride (GaN) substrates - on the way to p-type substrates" leaded by Tomasz Sochacki will be carried out in the Laboratory of Crystal Growth (NL3). It was on the podium of the ranking list of 41 projects qualified for funding!
• The project "Towards yellow laser diodes with tunable InGaN pseudo-substrate relaxation enabled by nanoporous GaN” leaded by Marta Sawicka will ba carried out in the Laboratory of MBE (NL14).

Congratulations!

The final ranking list of projects qualified for funding in the 14th competition of the LIDER Program is available on the website of the National Center for Research and Development.

Gallium nitride-based light-emitting diodes are the most energy-efficient light sources. Despite their clear advantages, they require a direct current (DC) power supply to operate effectively, while the power grid is built on alternating current (AC). An interesting proposal for a new class of optoelectronic devices dedicated to direct AC operation has been proposed by Mikołaj Żak together with colleagues from the Laboratory of Molecular Beam Epitaxy (NL-14) and other researchers of the Institute of High Pressure Physics PAS (IHPP PAS).

In a paper published in Nature Communications (Impact Factor 16.6), they present a bidirectional light-emitting diode (BD LED) that emits light in both directions of current flow through the device, unlike conventional LEDs, which must be forward biased. It is possible due to the special epitaxial structure of the BD LED, in which the active region is surrounded on both sides by tunnel junctions from the p-type doped regions. This ensures that electrons and holes are effectively injected into the same quantum well above the turn-on voltages under both negative and positive bias.

The paper "Bidirectional light-emitting diode as a visible light source driven by alternating current" (M. Żak, et al. Nat Commun 14, 7562 (2023)) is an important part of the upcoming PhD thesis of M.Sc. Mikołaj Żak and is the result of many years of research on tunnel junctions in GaN undertaken by the NL-14 group of IHPP PAS.

Instytut Wysokich Ciśnień Polskiej Akademii Nauk poszukuje kandydatów na stanowisko: Asystent/-ka Dyrektora.

Szczegóły oferty