GaN substrates of the highest structural quality for high-power electronics
Abstract
The main objectives of this projects are to develop the ammonothermal technology in order to obtain the highest structural quality 2 -inch gallium nitride (GaN) substrates and to improve the crystallization from gas phase to deposit homo-epitaxial layers of the hig hest purity on the mentioned substrates. Optoelectronic and electronic devices based on GaN are present in everyday life as well as in very specific applications or harsh environment as aircraft or spacecraft. With increasing global power requirements the demands for power semiconductors are also rising. GaN enables greater performance (including switching), higher efficiency as well as smalle r size of the devices. Though the devices are promising, the reliability and commercial success have been limited by the lack of nat ive substrates of high structural quality. Today, nitride-based devices, both optoelectronic and electronic, are built on foreign su bstrates. Moreover, the majority of commercially-available GaN wafers are prepared from crystals which are grown on non-native seeds . This leads to significant stress, deformation of crystallographic planes or high threading dislocation density (TDD). These factor s are detrimental for using GaN crystals as substrates for devices.The best technology for growing bulk GaN, in terms of structural quality, is ammonothermal. Ammonothermal-GaN (Am-GaN) crystals have flat crystallographic planes and TDD as low as 104 cm-2. N-type Am-GaN substrates can be applied for building electronic Field Effect Transistors (FETs). This kind of devices require a GaN layer o f the highest structural quality and purity. Gallium nitride of the highest purity can only be achieved by halide vapor phase epitax y (HVPE). Therefore, a combination of the HVPE technology with Am-GaN substrates is the best path to achieve GaN-on-GaN structures o f the highest crystallographic quality and the lowest donors and acceptors concentrations in the epitaxial layers. There are three a few specific objectives of the project:1. to improve the ammonothermal crystallization process through application of computational fluid dynamics (CFD) method for modeling convective flows of reagents, temperature distribution as well as supersaturation in the c rystal growth zone;2. to improve the wafering procedures, as slicing, grinding, drilling, lapping, polishing and CMP, needed for pre paring epi-ready substrates from crystals;3. to improve the HVPE crystal growth technology and deposit homo-epitaxial layers of the highest purity on Am-GaN substrates.Realization of presented objectives will allow us to: obtain the Am-GaN crystals uniform in ter ms of their thickness, TDD as well as concentrations of dopants and impurities; increase the yield and structural quality of 2-inch Am-GaN epi-ready wafers of (0001) surfaces with visible atomic steps and (000-1) surfaces protected against decomposition during lo ng epitaxial growth; crystallize GaN-on-GaN structures with epitaxial layers of the highest purity and without traps formed by unin tentionally incorporated dopants.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 22, 2021
- Source ID
- N629092112063
Entities
People
- Michal Boćkowski
Organizations
- Institute of High Pressure Physics, Polish Academy of Sciences
- Office of Naval Research
- United States Navy