News: Optoelectronics
2 November 2020
IQE develops IQGeVCSEL 150 technology
Epiwafer foundry and substrate maker IQE plc of Cardiff, Wales, UK has announced the development of IQGeVCSEL 150 technology for vertical-cavity surface-emitting lasers (VCSELs) on 6-inch (150mm) germanium (Ge) substrates, which it describes as a critical step in the pathway to 200mm and 300mm VCSEL technology.
VCSELs are a key component in telecom and 3D sensing systems. Applications include high-speed data-center infrastructure; facial recognition, proximity sensing, and light detection & ranging (LiDAR) time-of-flight sensors on mobile handsets; in-cabin and environmental sensing for autonomous drive vehicles; and 3D image recognition. As demand for VCSELs grows and technical requirements become more stringent, there is the need to scale to larger wafer diameters and demonstrate a path for integration with leading-edge CMOS technology, notes the firm.
IQGeVCSEL 150 is a key development milestone in addressing this, it adds. Germanium substrates are readily available in diameters up to 200mm and provide a clear route for VCSEL growth on silicon substrates (through the use of IQE’s Ge-on-silicon templates) up to 300mm.
IQE says that, using this unique, patent-pending technology, it has demonstrated device performance parity between identical VCSEL structures grown on Ge and conventional gallium arsenide (GaAs). While conventional growth of VCSELs on 200mm GaAs substrates is currently virtually impossible, the use of Ge removes this limitation because Ge substrates allow for optimal strain management, resulting in a VCSEL wafer that is ~10x flatter compared with VCSELs on GaAs.
This not only simplifies the subsequent wafer fabrication process but results in a wafer that is up to ~3x more uniform. The improved wafer flatness provides additional design flexibility for thicker device architectures required to access longer-wavelength VCSELs. Finally, Ge substrates are available with zero defect density, resulting in higher-quality VCSEL epitaxial material compared with GaAs.
“Demonstrating device parity with GaAs but with a more uniform VCSEL wafer and improved flatness is a highly significant milestone, and we have begun sampling with partners and customers,” says chief technology officer Dr Rodney Pelzel. “In addition, this provides clear line of sight to growth on larger-diameter wafers as well as VCSEL growth on silicon at 200mm and 300mm wafer sizes.”
