Substitutional synthesis of sub-nanometer InGaN/GaN quantum wells with high indium content

Area of Science:

• Semiconductor Physics
• Materials Science
• Nanotechnology

Background:

• Sub-nanometer Indium Gallium Nitride/Gallium Nitride (InGaN/GaN) quantum wells (QWs) are crucial for optoelectronics and topological insulator research in III-nitride semiconductors.
• Previous studies indicated a kinetic limit of 33% indium content in ultra-thin QWs, restricting their applications.

Purpose of the Study:

• To demonstrate the deposition of quasi two-dimensional (quasi-2D) InGaN/GaN QWs with indium content exceeding the established limit.
• To investigate the growth mechanisms governing ultra-thin QW formation and composition.

Main Methods:

• Plasma-assisted molecular beam epitaxy (MBE) was used to grow multi-QW heterostructures.
• Quantitative scanning transmission electron microscopy (STEM) with atomistic calculations determined composition and strain at monolayer resolution.
• Photoluminescence measurements corroborated compositional findings.

Main Results:

• Quasi-2D QWs with self-limited monolayer thickness were achieved.
• Indium content significantly exceeded the 33% limit, reaching nearly 50% under specific metal-rich growth conditions.
• A substitutional synthesis mechanism involving In/Ga exchange at surface sites was proposed.

Conclusions:

• The kinetic limit on indium content in ultra-thin InGaN/GaN QWs can be overcome.
• A novel substitutional synthesis mechanism explains the high indium incorporation.
• This work paves the way for advanced III-nitride materials, including binary Indium Nitride/Gallium Nitride (InN/GaN) quasi-2D QWs.