A WSe2 Photodiode Received Visible-Light Data at 10 Gbit/s

A visible-light photodetector built from tungsten diselenide and integrated directly with a thin-film lithium niobate waveguide received data at up to 10 Gbit/s. The experimental device combined a two-dimensional semiconductor junction with a photonics platform valued for routing and modulating light on chips.

Combining two difficult materials systems

Thin-film lithium niobate can guide light efficiently and supports high-performance optical modulation, making it attractive for integrated photonics. Detecting the light on the same platform is harder. Conventional detector materials can be difficult to integrate without compromising the waveguide or adding complex processing.

The team placed a lateral p-i-n photodiode made from the two-dimensional semiconductor WSe2 alongside the lithium-niobate waveguide. A self-aligned doping process defined the differently doped regions and reduced slow carrier diffusion and trapping. The researchers also engineered selenium vacancies and used a molybdenum-oxide buffer layer to form n-type and p-type ohmic contacts.

The result combines strong visible-light response with data reception on a photonics platform, but its highest data-rate figure should not be confused with the measured 3 dB bandwidth.

What the measurements mean

The paper reports carrier mobilities above 350 cm² per volt-second for both electrons and holes. Faster carrier motion helped the detector reach a measured bandwidth of 1.12 GHz. The authors separately demonstrated visible-light data reception at rates up to 10 Gbit/s, a communications test that depends on the complete signal chain and modulation format as well as the detector.

At a wavelength of 638 nm, the device reached a responsivity of about 492 mA/W. Its external quantum efficiency approached unity at 95.6%, indicating that a high fraction of incident photons contributed collected charge under the reported conditions.

The work sits beside broader efforts to process light directly on chips. NewTqnia previously reported a photonic chip that separated hidden modes in mixed light. That device performed an optical transformation; the new detector instead converts guided visible light into an electrical signal for receiving data.

Where it could fit

Visible-light integrated photonics can serve sensing, displays, quantum systems and short optical links where silicon detectors are not always the best match. Integrating a responsive two-dimensional detector with lithium niobate could reduce the need to route light off chip for conversion.

The next tests should quantify device-to-device variation, long-term stability, receiver sensitivity and energy per bit in a complete link. Demonstrating arrays and scalable fabrication would be especially important. The present work establishes a high-performing detector architecture and a 10 Gbit/s laboratory reception result, while leaving packaging and manufacturing as the next major hurdles.