A Wafer-Scale, Low Defect Density Strain Relaxed Template for III-Nitride-Based High Efficiency and High-Power Devices

Background

The bandgap of InGaN-based III-nitride alloys span across a wide range, and they are promising for applications in electronic and optoelectronic devices. The wide spectrum from visible to NIR of InGaN-based emitters can serve as the light source for atomic clocks and atom cooling and trapping. Additionally, integration of III-Nitride LDs with photonic circuit platforms can enable chip-scale optics system, including optical clocks, imaging and sensing, quantum computing, and more. However, there is a large lattice mismatch in this material system. This mismatch causes high strain for InGaN grown on GaN, resulting in generation of dislocations and degradation of surface morphology. The high threading dislocation density (TDD) generated from the large lattice mismatch serves as non-radiative recombination center, causing a drastic degradation in quantum efficiency as well as device lifetime. All these issues hinder the development of InGaN-based emitters, and it is therefore critical to address the high strain issues.

Description

Researchers at the University of California, Santa Barbara have devised a novel method of producing a wafer-scale, low defect density, strain relaxed template (SRT) for III-nitride-based devices. By utilizing a thin, highly defective III-nitride decomposition layer beneath a strain relaxed layer, followed by patterned etching and regrowth via lateral overgrowth, this approach dramatically reduces threading dislocation density and strain across large wafer areas. The method uniformly relaxes strain while maintaining low defect densities, enabling high efficiency and longer lifetime for devices such as LEDs, laser diodes (LDs), field effect transistors (FETs), and heterostructure FETs. Compared to prior approaches, it offers uniform relaxation over an entire wafer without limiting usable device area, solving longstanding issues related to lattice mismatch and strain-induced defects in InGaN-based materials.

Advantages

• Uniform strain relaxation across wafer-scale substrates (2 inches or larger)
• Significantly reduced threading dislocation density to near substrate levels
• Enables growth of high indium composition InGaN layers with fewer compositional pulling effects
• Improved surface morphology and reduced cracks
• Full wafer usability due to uniform strain relaxation and lateral overgrowth coalescence
• Longer device lifetimes owing to reduced non-radiative recombination and carrier leakage
• Highly suitable for scalable, cost-effective industrial production

Applications

• High efficiency and high power light-emitting diodes (LEDs) spanning visible to near-infrared spectrum
• Laser diodes (LDs) for blue, green, red, and near-infrared applications including displays and sensing
• Field effect transistors (FETs) and heterostructure FETs for high-power electronics
• Photonic integrated circuits enabling chip-scale optical systems such as optical clocks, quantum computing, and imaging
• Quantum technology devices requiring stable and efficient III-nitride light sources

Patent Status

Additional Patent Pending