Growth of nitride-based heterostructures for advanced scintillators and HEMTs and their characterization by optical and transport methods (in the frame of project OP-PK LABONIT)


Semiconductor nitride-based heterostructures intended for advanced scintillators and high electron mobility transistors (HEMT) are prepared using metal-organic vapour phase epitaxy (MOVPE) technique. Optimization of both types of structures cannot be achieved without close feedback between technology and characterization. As-grown structures are thus tested as soon as possible by means of optical (Raman, photoluminescence, cathodoluminescence) and transport (conductivity, Hall, C-V profiling) methods.

MOVPE apparatus AIXTRON – CCS3´2 for the growth of nitride-based heterostructures.

The project encompasses two topics:

  • Development of thick luminescence heterostructures with multiple InGaN/GaN quantum wells
  • Development of nitride transistor heterostructures for power applications

Development of thick luminescence heterostructures with multiple InGaN/GaN quantum wells

Development of thick luminescence heterostructures with multiple InGaN/GaN quantum wells
The topic involves the development of scintillation heterostructures with ultrafast, sub-nanosecond luminescence response to ionizing radiation, made from nitride semiconductors by means of organo-metallic epitaxy. This technological approach enables preparation of material in which atoms are arranged into a crystalline lattice, however individual layers of this quasi-monocrystal can have different chemical composition. Through interleaving such thin layers on the atomic scale, it is possible to prepare quantum heterostructures with diverse functionalities, which find their use in high-tech industrial and healthcare applications. One of the biggest related challenges is to prepare heterostructures with high number of quantum wells in their active layer, so that as large portion as possible of the deeply penetrating ionizing radiation is detected. The technological and luminescence research groups closely cooperate on development of these heterostructures, and they also cooperate with the Crytur company in Turnov.


Left: A snapshot from a transmission electron microscope with atomic resolution, showing a heterostructure with InGaN quantum wells (darker areas). The thickness of quantum wells is roughly 2 atomic layers.
Right: A photograph of heterostructure prepared on 2” sapphire substrate, emiting light under UV illumination.

Development of nitride transistor structures for power applications

Nitride semiconductors present an ideal material for high-power applications owing to their wide band gap, high thermal conductivity and excellent thermal stability. Moreover, their built-in piezoelectric fields allow one to prepare heterostructures featuring two-dimensional electron gas exhibiting high electron mobility, which makes them suitable for high-frequency operation. Development of these transistor structures is conducted in cooperation with the On Semiconductor company in Rožnov pod Radhoštěm. The structures are numerically modelled, prepared using the MOVPE technology and characterized using luminescence and transport measurements. Cooperation on this topic involves the technological and luminescence, as well as transport research groups.

Schematic of a HEMT structure
Dep14_HEMT struktura.png

Schematic of a HEMT structure. An example of the developed heterostructures for transistors with high electron mobility

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