Update Light Triggered Thyristor RD Janusz Rodziewicz TEABTEC

Update Light Triggered Thyristor R&D Janusz Rodziewicz (TE-ABT-EC)

Presentation Overview Brief reminder about SCR turn-on • Max di/dt crude estimate • Optical absorption depth • High power laser selection • • Proof of concept test bench 9/15/2020 Light Triggered Thyristor R&D 2

SCR Switching Turn-on Figure Turn-on transient waveforms [POWER SEMICONDUCTORS AND PULSE POWER, Wiliam M. Portnoy, 22 nd International Power Modulator Symposium, June 1996] Figure Structural details of a generic thyristor (a) vertical cross section; (b) gate and cathode layouts; (c) circuit symbol. [NED MOHAN, TORE M. UNDELAND, “POWER ELECTRONICS AND DRIVES”, SECOND EDITION, JOHN WILEY & SONS, INC. ] 9/15/2020 Light Triggered Thyristor R&D 3

Light Triggered Turn-on In Production - Low Inductance thyristor clamp • Optimised for extremely high current rise rates • Promising SCR 2. 5 k. V Device to be tested IXYS WESTCODE Y 502 NC 250 PARAMETER LOW COST POWEREX T 8 K 7 T 82 Repetitive peak revers voltage Maximum pulse current Critical rate of current rise Turn-on time Capsule diameter Nominal gate trigger current Figure Commutation waveforms obtained with very sever activation pulses M 1&M 3 – associated currents; M 2&M 4 –associated anode-cathode voltages HIGH PERFORMANCE IXYS WESTCODE Y 5002 NC 250 4500 V 2000 V 5. 5 k. A (8 ms) 50 k. A (250 us) 0. 5 k. A/us 11 k. A/us 2 us 52 mm 200 m. A 1 us 67 mm 80 A (100 A/us) 9/15/2020 Document reference 4

Max di/dt Crude Estimate (a) (b) Max di/dt Crude Estimate for a fast exponential Vak fall (previous slide) and Cv = 1. 75 Joule/(°C-cm 3) 24. 5 k. A/μs Figure distribution POWEREX gate Device form w=1 mm, h=6 mm, r=2. 5 mm (a) View of extracted wafer from the capsule (cathode and gate electrode view). Grey area is the conducting are at t, us is turn-on spreading velocity 9/15/2020 assuming initial blocking voltage Vak 0=4 k. V and d. Tjmax=135 C from initial room temperature of 25 C Light Triggered Thyristor R&D 5

When the light hits a layer it is reflected, refracted, and absorbed in a way that can be derived from the Fresnel equations. Analysis underlying the transfer –matrix method: real and imaginary refractive index of silicon 8 7 100 6 10 0. 65 x 1/e 1 0. 4 0. 5 0. 6 0. 7 0. 8 0. 9 1 1. 1 Wavelength [μm] Figure Optical absorption depth as a function of optical wavelength. 4 3 1 0 200 300 400 500 600 700 800 900 10001100120013001400 1. 1 x 1/e A 5 2 Relation of absorption coefficient (α) and light intensity (I) (Lambert-Baer´s Law) : [1/length] reflectivity Silicon absorption length [μm] 1000 Figure Sample calculation of local absorption in silicon with air on both sides. Done for two wavelengths: 900 nm and 1000 nm wavelength (nm) Figure [Green, M. A. and Keevers, M. "Optical properties of intrinsic silicon at 300 K ", Progress in Photovoltaics, p. 189 -92, vol. 3, no. 3; (1995)] [Script “Multilayer optical calculations” Steven J. Byrnes Cambridge, Massachusetts, USA] SCR Forward Blocking VAK > 0 IGate = 0 A 6

High Power Laser Modules overview AKELA ALC-1070 -500 Laser Components Pigtailed Diode Quantel Stack QD-Q 6 R 12 -DO DILAS IS 28. 9 Peak Power 600 W 65 W (100 W custom) 2500 W (Total) 500 W Wavelength 1000 nm 905 nm 980 nm 940 nm Max Single Pulse Peka Duration 200 ns 150 ns 5 us Fiber-Coupled NO YES YES No. of optical outputs 1 1 10 (150 W per Fiber) 1 Unit Price ~2 k euros ~250 euros 43 k euros – development (NRD) 14 k euros – production 7. 5 k euros 9/15/2020 Light Triggered Thyristor R&D 7

Selected Laser Components Pigtailed Diode Source LDP-V 80 -100 V 3. 3 Driver module for pulsed lasers 9/15/2020 Light Triggered Thyristor R&D 8

Proof of Concept Test Bench We intend to turn-on two stacked SCR thyristor wafers using laser activation. Diffusers are the key development, their evaluation will be performed on measurement test bench. Furthermore it is expected to improve significantly device switching characteristics (w. r. t. datasheet) expressed in parameters such as turn-on delay and maximal current rise rate Figure Overview - 3 D model of 1” fused silica diffuser placed in its housing Figure Proof of concept configuration. View of stacked thyristor wafers overlapped with its diffusers Key Development - Diffusers allow light to scatter freely within the diffuser volume, activating whole available thyristor surface. Light enters through three independent optical inputs. Two types of diffusers have been designed and are in prototyping phase: • • 1” 3 D Printed 1” Fused Silica Figure SCR Stack Assembly view Figure Overview - 3 D model of 3 D Printed diffuser with inserted INOX pins Even 5 mm/k. V can be expected + interconnections with external circuit Light Triggered Thyristor R&D

Proof of Concept Test Bench Safety The bench inspected by TE Department Laser Safety Officer laser is registered as ISI 721 In order to minimise the risk of laser accidents, a interlocked safety enclosure system will be installed. 375 mm 660 mm 450 mm 300 mm 525 mm • Optical Enclosure features black hardboard panels that block stray light. Enclosure will interlock the laser power supply at the contact with aluminium breadboard, so that optical power won’t be available unless the test is enclosed. • These solid aluminium, nonmagnetic baseplates provide a convenient and cost-effective platform for assembling prototype optical assemblies, conducting experiments, and mounting small subsystems. They are finished with a black, minimally reflective anodized coating and are through-drilled with a standard 1" (imperial) or 25 mm (metric) hole pattern offset 1/2" or 12. 5 mm, respectively, from the edges of the board. The holes are threaded completely through these breadboards, allowing components to be mounted on both sides at once. • Laser energy detector Gentec QE 8 SP will be required to confirm the presence of the energy at the optical output YES/NO so that in case laser diode failure we won’t precede to the next stage and hold up the test https: //www. thorlabs. de/newgrouppage 9. cfm? objectgroup_ID=45 Light Triggered Thyristor R&D

Proof of Concept Test Bench Diffuser Measurement Scattered rays originating from the diffuser are expected not to be paralleled Detectors with larger aperture diameters (>8 mm) are generally not able to measure such low energy or power levels, due to the dramatically higher noise levels. The quoted QE 8 detector is the only suitable detector for this application. Focusing of diffuser output beam into the detector aperture is required. D θ Worst case angle θ Plano-Convex Lens Ø 1" f = 25. 4 mm Also it is planned to compare transmitted energy of different diffusers to 1” 250 um silicon wafer. The wafer temperature evolution will be measured under long time exposure to CW laser The APM(D) (201848) is designed to provide a stable, quiet DC voltage to our analog and digital, amplified power and energy probes. Light Triggered Thyristor R&D

Thank You for Your Attention! Questions? 9/15/2020 Light Triggered Thyristor R&D 12