From Handsets to 1.6T — The Week Taiwan's Compound Semis Found Their AI Customer

Taiwan's compound-semi bench gets a second cycle

The headlines this week were TSMC at NT$2,400, the TAIEX at a record 45,809, and a memory super-cycle that doubled NOR Flash and SLC NAND contracts in H1. Below all that, in the same three days, Taiwan's compound semiconductor layer — GaAs, SiC, GaN, optical epi — quietly shifted away from the handset cycle and onto the AI rack. Five separate Taiwan companies disclosed AI-side design-ins, capacity plans, or revenue pivots in 72 hours. That density isn't a coincidence.

The clearest signal came from Win Semi (3105). On 6/16 the company said its AI optical epi-wafer business is in small-volume 200G receiver production, with the next step being 1.6T datacenter modules. This isn't a sidecar product; it's a category swap. The company whose fate was tied to the smartphone RF cycle is moving its primary epi line to AI optical, where 1.6T is the candidate standard for 2026-2027 hyperscale buildouts. For a name that had been a handset cycle proxy, the 2027 revenue mix is about to be unrecognizable.

The same day, at a SEMI power-semiconductor forum, Episil told the audience that the migration to 800V HVDC architectures in hyperscale AI data centers is now driving meaningful SiC and GaN demand. Earlier-gen data centers ran 12V/48V DC busses, but GB200- and MI450-class racks pushing past 100kW per rack forced consensus that 800V HVDC is the only practical path forward. The 800V conversion stage cannot use silicon MOSFETs — it needs SiC and GaN devices, which Episil and the broader Taiwan compound-semi bench supply.

Signal three came from Everlight (2393). At its 6/13 shareholder meeting the company disclosed that its optocouplers and SiC products have been designed into Delta (2308) and Lite-On's AI server power supplies. Optocouplers are compound-semi isolation components, critical at 800V where the digital control side must be galvanically separated from the high-voltage power side. Delta and Lite-On are the dominant PSU suppliers for Nvidia's GB200 and MI450 racks, so Everlight just captured a per-rack BOM line that scales with the AI rack ramp.

On the optics side, Largan disclosed on 6/13 that it will complete its first fully automated CPO fiber-array pilot line in September with sub-0.3μm precision. And on 6/15, Hon Chin (7769) told shareholders it would expand capacity 40% in 2026 and another 30-50% in 2027, with CPO test-gear samples in Q4. Optical materials, precision assembly, and test gear — three layers of the optical chain — all showed 2026-2027 capacity in the same week.

Why now, and why all at once

The unifying fact for these five names — Win Semi, Episil, Everlight, Largan, Hon Chin — is that the AI rack just opened a new BOM line that didn't exist a year ago. Silicon at the top (TSMC, MediaTek) is already priced in. What isn't priced in is what surrounds it: GaAs optical epi, SiC power, GaN converters, optocouplers, CPO fiber arrays. The market has not calibrated how much per-rack BOM accrues to compound semis as racks scale.

The motivating backdrop is the memory message Jensen Huang carried at Computex — "memory shortage has no end in sight" — repeated three times. The same week, JPMorgan took Winbond to a Street-high NT$255 and TrendForce reported NOR Flash and SLC NAND contracts doubling in H1 because the Korean majors are vacating mature-node capacity into HBM. The shape of the cycle is now: AI PCs go from 32GB to 128GB baseline (4×), HBM eats mature-node fabs, and everything left over re-prices. The compound-semi parallel is structurally identical: the AI rack adds optical and 800V power stages, which add compound-semi BOM per rack, while the existing handset/IoT base business hasn't shrunk.

Taiwan's structural advantage is that the compound-semi bench is intact across all four sub-categories — RF (Win Semi), power (Episil), optical (Largan, Hon Chin), isolation (Everlight). Korea's memory-heavy model concentrates the cycle; Taiwan's distributed compound-semi base spreads it. Chosun Biz noted on 6/15 that this is why Taiwan's AI-boom hiring data is outpacing Korea's — and the same diagnosis applies to revenue distribution.

What the report tracks

Win Semi (3105) is the cleanest expression but the least priced-in. As RF epi gets displaced by AI optical epi, the P&L will go through a decoupling phase where the mix moves before the absolute revenue inflects. If 1.6T volumes ramp in 2027 as the company implied, the 2027 revenue mix will be unrecognizable from 2024. Delta (2308) and Hon Hai (2317) — both 800V-PSU and rack-level partners; Foxconn announced a Schneider Electric AI-DC architecture deal on 6/15 — are priced for this. The compound-semi suppliers inside their bills of materials are not. Largan, Hon Chin, and the CPO chain will show first real revenue visibility in September and Q4.

The deeper signal is that this is the first week the market saw — across five separate disclosures in 72 hours — that an AI rack cannot be built from silicon alone. Taiwan's compound semiconductor layer just started running on its own cycle, independent of TSMC's wafer cadence.

Key Sources: - Win Semi Eyes AI Optical Comms Growth as Epi-wafer Demand Upgrades to 1.6T (cnyes, 2026-06-16) - 800V HVDC Data Centers Lift SiC/GaN Demand, Episil Cites Compound Semi Tailwind (technews, 2026-06-15) - Everlight optocouplers, SiC win design-ins at Delta & Lite-On AI server PSUs (cnyes, 2026-06-13) - Largan to unveil first CPO fiber-array pilot line in September, sub-0.3μm precision (technews, 2026-06-13) - Hon Chin Plans 30-50% Capacity Expansion in 2027; CPO Test Gear Samples in Q4 (cnyes, 2026-06-15) - plus 2 more