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Exploring the Design and Measurements of Next-Generation 4H-SiC LGADs

Peter Švihra, Jan Chochol, Vladimír Kafka, Adam Klimsza, Adam Kozelsky, Jiří Kroll, Roman Malousek, Mária Marčišovská, Michal Marčišovský, Marcela Mikeštíková, Michael Moll, David Novák, Radek Novotný, Peter Slovák, Radim Špetík, Moritz Wiehe

TL;DR

This work extends LGAD technology to the wide-bandgap 4H-SiC to enable fast timing in radiation-tolerant environments by introducing an internal gain layer. The authors fabricate 3x3 mm^2 LGADs on 6-inch N-type substrates with an implanted gain region and perform comprehensive IV/CV, TCT, and beta-source tests, confirming stable high-voltage operation and appreciable charge multiplication. A key result is that one device (LGAD1_45) achieves sub-100 ps timing with a gain near 20, validating the viability of 4H-SiC LGADs for high-radiation timing detectors, while another variant (LGAD2_34) requires further optimization. The findings point to the potential of 4H-SiC LGADs for applications in high-energy physics and related fields, with future work focusing on doping optimization, device geometry, radiation resilience, and extended test-beam campaigns.

Abstract

This contribution presents the design, production, and initial testing of newly developed 4H-SiC Low Gain Avalanche Detectors (LGADs). The evaluation includes performance metrics such as the internal gain layer's efficiency in enhancing signal generation. Initial laboratory and Transient Current Technique (TCT) measurements provide insight into the device's stability and response to the signal. Due to the increase of availability provided by the industry, 4H-SiC is emerging as a strong candidate for the next-generation of semiconductor detectors. Such sensors are promising due to the inherent radiation tolerance of 4H-SiC and its stable operation across a wide temperature range. However, due to the wider-bandgap of 4H-SiC compared to standard silicon, and difficulty to produce high-quality layers thicker than 50 \textmu m, an internal charge multiplication layer needs to be introduced. The presented 4H-SiC LGADs, fabricated by onsemi, are optimized for an N-type substrate and epi wafer. The initial TCT and laboratory test results demonstrate fast charge collection and uniform multiplication across multiple samples produced on a single wafer.

Exploring the Design and Measurements of Next-Generation 4H-SiC LGADs

TL;DR

This work extends LGAD technology to the wide-bandgap 4H-SiC to enable fast timing in radiation-tolerant environments by introducing an internal gain layer. The authors fabricate 3x3 mm^2 LGADs on 6-inch N-type substrates with an implanted gain region and perform comprehensive IV/CV, TCT, and beta-source tests, confirming stable high-voltage operation and appreciable charge multiplication. A key result is that one device (LGAD1_45) achieves sub-100 ps timing with a gain near 20, validating the viability of 4H-SiC LGADs for high-radiation timing detectors, while another variant (LGAD2_34) requires further optimization. The findings point to the potential of 4H-SiC LGADs for applications in high-energy physics and related fields, with future work focusing on doping optimization, device geometry, radiation resilience, and extended test-beam campaigns.

Abstract

This contribution presents the design, production, and initial testing of newly developed 4H-SiC Low Gain Avalanche Detectors (LGADs). The evaluation includes performance metrics such as the internal gain layer's efficiency in enhancing signal generation. Initial laboratory and Transient Current Technique (TCT) measurements provide insight into the device's stability and response to the signal. Due to the increase of availability provided by the industry, 4H-SiC is emerging as a strong candidate for the next-generation of semiconductor detectors. Such sensors are promising due to the inherent radiation tolerance of 4H-SiC and its stable operation across a wide temperature range. However, due to the wider-bandgap of 4H-SiC compared to standard silicon, and difficulty to produce high-quality layers thicker than 50 \textmu m, an internal charge multiplication layer needs to be introduced. The presented 4H-SiC LGADs, fabricated by onsemi, are optimized for an N-type substrate and epi wafer. The initial TCT and laboratory test results demonstrate fast charge collection and uniform multiplication across multiple samples produced on a single wafer.

Paper Structure

This paper contains 11 sections, 9 figures.

Table of Contents

  1. Introduction
  2. Design and Fabrication of 4H-SiC LGADs
  3. Experimental Setup
  4. IV and CV Measurements
  5. Transient Current Technique (TCT)
  6. Beta-Source Setup
  7. Results
  8. IV and CV Measurements
  9. TCT Analysis
  10. Beta-Source Performance
  11. Conclusions

Figures (9)

  • Figure 1: Comparison of current on voltage dependencies for no-gain PN diode and two types of LGADs from W19. Each type measured for around 20 samples plotted as mean (solid) with stdev (shaded). Sharp increase above 100V matches gain layer depletion.
  • Figure 2: Comparison of voltage dependency of $1/C^2$ (left axis, solid) and $C$ (right axis, dashed) for no-gain diode and two types of LGADs from W19. Each type measured for around 20 samples plotted as mean with stdev (shaded).
  • Figure 3: Full depletion voltage for different device types (PN, LGAD1, LGAD2) across three wafers (30µm thick W16, and 50µm thick W17 and W19). Each point represents the fitted full depletion voltage with error bars indicating standard deviation and adjacent values specifying the number of measured samples.
  • Figure 4: Transient signal response of a 4H-SiC diodes to UV pulse under different bias voltage. Each line is averaged from multiple measurements.
  • Figure 5: Voltage dependency of gain calculated as a ratio of total signal of selected W19 LGAD samples and no-gain W19_PN_21 diode from the same wafer. Measured using TCT, total signal calculated as integral of the transient pulse.
  • ...and 4 more figures