Wide Bandgap Materials

Wide bandgap (WBG) materials are essential for the next generation high-efficient electronics. They are critical in enhancing the speed, efficiency, and performance of key applications such as power conversion, communications and lightings. Recent technological trends show that there is a driving need to minimize power conversion losses in electronic modules, with SiC and GaN offering higher breakdown voltage devices with lower weight and fast switching. IMRE has been engaged in WBG electronics research since 2009. Hence, we have more than 60 publications, 7 IPs and the research teams are actively engaged with industry players in this area of work. We have a team with good expertise in the growth of WBG materials including their characterization, defect analysis, and device prototyping to improve performances. Our research efforts are focused on the 200 mm diameter substrate and epitaxial growth with process integration directed toward GaN and SiC electronic devices.
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MOCVD related epitaxial development work of 200 mm GaN on Si and capabilities for structural, optical and electrical characterization.

Capabilities


Our highly dedicated team has plenty of research experience in WBG materials, WBG devices and their process development. We are relentless in building our expertise and capabilities in WBG and below are a comprehensive list of expertise we have been developing over the years:

  • 200 mm MOCVD for GaN: Epitaxial growth with wafer level characterization, defect analyses, in-situ SiN passivation, buffer structure optimization, in-situ curvature profiling, and scaled-up processes for power/RF device demonstration
  • 200 mm bulk SiC growth: 4H-SiC bulk growth with low defects and defect reduction R & D on SiC wafers from 150 to 200 mm PVT growth
  • 200 mm SiC Epitaxy:  R & D on SiC epiwafers with thickness suitable for 1200-3300 V device application potential
  • In-situ Multi-Wavelengths Reflectance/Curvature profiling: In-situ growth monitoring for wafer bow control with structural and electrical homogeneity
  • Microcavities, DBR layers Design and Growth: Capabilities for III-V and dielectric DBR for microcavity based display application
  • 200 mm HRXRD: Rocking curves for tilt and twist, Fast wafer level reciprocal space mapping (RSM), Wafer level x-ray reflectivity (XRR)
  • Wafer level UV-Vis, Micro PL, Micro Raman scattering on WBG materials
  • Electrical device measurements (up to 3 kV)

Capabilities
Blue LED epitaxial growth on 200 mm Si(111) and related studies to improve quantum efficiency of layers. IMRE uses an advanced x-ray diffractometer that is perfectly suited for delivering complete 200 mm high-resolution XRD wafer mapping and fast reciprocal space mapping with the high-end solid-state detector. These maps indicate the uniformity of both substrate wafers and the hetero-epitaxial layers grown upon them, by measuring substrate and layer peak position, width and intensity, composition and strain.

Highlight & Achievements

The team has worked well with the industry, start-up ecosystem, and universities to develop and commercialize WBG related technologies. We will be happy to engage and work with interested partners in either exploratory or applied research. Some of our R & D achievements and interests are highlighted below.


Epitaxy solutions for GaN on Silicon high voltage electronics:

  • Developed AlN buffer layer between GaN and Si to overcome the melt-back etching/reduce stress, use of multiple intermediate layers to reduce the crack and defect density, epitaxy process tuning to increase buffer breakdown for high voltage devices, 200 mm AlGaN/GaN HEMT epiwafer with Au-free transistors ON-OFF ratio >109, high buffer breakdown structures upto 1000 V and 650 V HEMT devices with gate leakage current <nA/mm, reliability tests with lower channel temperature in HEMTs, and sensors using GaN on Si HEMTs.
  • The team has demonstrated unique AlN epitaxy to reduce Al/Ga diffusion and reduced auto-doping at AlN/HR-Si for RF HEMTs, demonstration of InAlN/GaN-on-Si transistor wafers for fmax >100 GHz for high frequency operation and InAlN/GaN FIN-HEMTs.
  • Developed monolithic AlGaN/GaN and InAlN/GaN HEMT-UV detector structures on Si exhibiting ultra-high responsivity > while maintaining a photo to dark current ratio suitable for UV sensing application
  • Current on-going research on E-mode HEMTs to define technical roadmap for high yield chip production using 200 mm GaN on Si technologies.

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STEM imaging of HEMT stack and 1.0 µm ×1.0 µm AFM roighnroughness of about 0.1 nm 

Fig. 3. 200 mm AlGaN/GaN HEMT on Si(111) and related studies to increase breakdown voltage at a lower gate to drain spacing,. The ultrasmooth f HEMT epilayers are achieved by tight control of inetrfaces duing MOCVD processes. 

Technology development toward 200 mm 4H-SiC Power Electronics:

SiC power electronics has demonstrated improved efficiencies, reduced size, and reduced weight when compared to conventional Si technology. But mass scale technology deployment needs extensive R & D on large diameter 4H-SiC. Our current R & D is focused on 200 mm SiC solution toward 10 cents/A for 100 A switches and SiC front-end processes for 1200-3300 V applications.

  • The Phase I of our proposal is focused on the defect reduction R & D and commercialization possibilities with 150 - 200 mm substrates and epiwafers development, with a target micro-pipe density <1 cm-2 in bulk, and with a TSD target <300 cm-2  in epiwafers.
  • Development of 4H-SiC using modified physical vapour transport processes, crucible customization for SiC ingots, wafer manufacturing by dicing/grinding/polishing with materials characterization support using HRXRD, XRT, FTIR, AFM, Optical inspection: micro-PL, micro-Raman, electron microscopy: SEM, TEM, STEM-EELS/CL, and electrical characterization with breakdown voltage testing on 1200-3300 V epiwafers.
  • The Phase II of this SiC program is seeking industry partnerships and cooperation interests to develop 1200-3300 V rated 4H-SiC MOSFETs for power switches, with a focus on device manufacturing in Singapore and reliability qualifications for usage in transport, renewables and micro-grids.

Contact

Dr. Tripathy Sudhiranjan, tripathy-sudhiranjan@imre.a-star.edu.sg

Dr. Chiam Sing Yang, chiamsy@imre.a-star.edu.sg

General: industry@imre.a-star.edu.sg

We welcome queries and collaboration partners for both the research and commercialization of wide bandgap materials related processes, technologies and devices.