Strain-Controlled Recombination in InGaN/GaN Multiple Quantum Wells on Silicon Substrates

Area of Science:

• Materials Science
• Optoelectronics
• Semiconductor Physics

Background:

• Indium Gallium Nitride/Gallium Nitride (InGaN/GaN) multiple quantum wells (MQWs) are crucial for light-emitting diodes (LEDs).
• Growth on silicon substrates presents challenges due to lattice mismatch and thermal expansion differences, leading to strain.
• Controlling strain is vital for optimizing LED performance and reliability.

Purpose of the Study:

• To investigate the impact of tensile stress on the photoluminescence (PL) properties of InGaN/GaN MQW LEDs.
• To explore strain-controlled recombination mechanisms in LEDs grown on silicon.
• To enhance the external quantum efficiency (EQE) of InGaN/GaN LEDs through stress management.

Main Methods:

• Fabrication of InGaN/GaN MQW LEDs on silicon substrates with varying tensile stress-controlling architectures.
• Utilizing periodic Si delta-doping and InGaN/AlGaN layer insertion to modify strain.
• Characterization of photoluminescence (PL) properties, including external quantum efficiency (EQE) and recombination rates.

Main Results:

• Samples with released tensile stress exhibited significantly improved PL performance, with EQE reaching 17% (a 7-fold increase).
• Reduced non-radiative recombination rates ((2.5–2.8)×10⁻² s⁻¹) were observed in stress-released samples, correlating with better crystalline quality and fewer defects.
• More stable and higher radiative recombination rates ((5.7–5.8)×10⁻³ s⁻¹) at room temperature were attributed to the suppression of shallow localized states.

Conclusions:

• Tensile stress management is a key factor in enhancing InGaN/GaN MQW LED performance on silicon.
• Optimized strain engineering leads to reduced non-radiative recombination and improved radiative efficiency.
• The findings provide a pathway for developing high-efficiency LEDs on cost-effective silicon substrates.