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Plasma-assisted Molecular Beam Epitaxy of N-polar InAlN-barrier High-electron-mobility Transistors
Published on: November 24, 2016
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Mg Doping of N-Polar, In-Rich InAlN
Ján Kuzmík1, Ondrej Pohorelec1, Stanislav Hasenöhrl1
1Institute of Electrical Engineering, Slovak Academy of Sciences, 831 04 Bratislava, Slovakia.
Materials (Basel, Switzerland)
|March 29, 2023
Summary
This study investigates magnesium doping in Indium Aluminum Nitride (InAlN) using Metal Organic Chemical Vapor Deposition. High doping levels degrade InAlN properties, increasing resistivity and reducing electron mobility.
Area of Science:
- Materials Science
- Semiconductor Physics
- Inorganic Chemistry
Background:
- Indium Aluminum Nitride (InAlN) is a crucial material for high-frequency electronics.
- Controlling p-type doping in InAlN is challenging but essential for device performance.
- Magnesium (Mg) is a common p-type dopant, but its effects on InAlN properties require detailed study.
Purpose of the Study:
- To investigate the effects of magnesium (Mg) doping on the structural, electrical, and optical properties of N-polar InAlN grown by Metal Organic Chemical Vapor Deposition (MOCVD).
- To determine the optimal Mg doping concentration for achieving desired InAlN characteristics.
- To understand the mechanisms behind property degradation at high doping levels.
Main Methods:
- N-polar In0.63Al0.37N thin films were grown on sapphire substrates using MOCVD.
- P-doping was achieved using bis(cyclopentadienyl)magnesium (Cp2Mg) with varying flow rates.
- Structural characterization included X-ray Diffraction (XRD).
- Electrical properties were measured via Hall effect and resistivity measurements.
- Optical properties were analyzed using photoluminescence (PL) spectroscopy.
Main Results:
- Mg doping introduced pits and degraded the surface morphology at higher concentrations.
- XRD analysis indicated phase separation and increased dislocation density with increasing Cp2Mg flow.
- Degenerate n-type conduction with free carrier concentrations of ~1019 cm-3 was observed.
- Electron mobility significantly decreased from ~40 cm2/Vs in undoped samples to ~0.3 cm2/Vs at the highest doping level.
- Resistivity increased by two orders of magnitude, reaching ~0.5 Ωcm.
- Photoluminescence showed a 0.22 eV red shift with Mg doping.
Conclusions:
- High Mg doping levels in InAlN lead to significant degradation in structural quality, electrical conductivity, and optical properties.
- Scattering from ionized Mg-related acceptor/donor levels is the primary cause of mobility degradation.
- The study highlights the challenges of achieving controlled p-type doping in InAlN and suggests limitations for high-power device applications.
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