19 May 2020
SweGaN’s buffer-free GaN-on-SiC HEMT epi demonstrates competitive microwave performance and device efficiency
SweGaN AB of Linköping, Sweden, which manufactures custom gallium nitride on silicon carbide (GaN-on-SiC) epitaxial wafers (based on a unique growth technology) for RF and power electronics devices, has announced a new benchmark for GaN high-frequency devices based on its QuanFINE material, reckoning that the demonstration promises commercial benefits for the entire GaN RF value chains including telecom, space, and military markets.
In a new joint study with the the Department of Microtechnology and Nanoscience at Chalmers University of Technology in Gothenburg, SweGaN explored QuanFINE epiwafer performance, based on GaN high-electron-mobility transistor (HEMT) technology at Chalmers (Chen et al, IEEE Electron Device Letters, DOI: 10.1109/LED.2020.2988074).
Collaborating with scientists at the university, the team performed a new benchmark comparing the conventional 1.8µm-thick Fe-doped GaN buffer epi-structure to SweGaN’s ‘buffer-free’ QuanFINE GaN HEMT heterostructures for microwave applications. The study revealed that the new concept, using a total GaN layer thickness of 250nm, does not compromise the material quality and device performance. Further, the device results indicate that the ‘buffer-free’ QuanFINE material can outperform conventional materials at the device level in the long run.
SweGaN says that, for customers and manufacturers, the ultimate benefits resulting from the new ‘buffer-free’ concept include lower trapping, better carrier confinement and lower thermal resistance, which could lead to higher device power efficiency and better reliability of GaN high-frequency devices.
“The new QuanFINE concept possesses many interesting features that are very attractive for both high-frequency and power electronics, says Niklas Rorsman, research professor at Chalmers. “As an example, the possibility of a pure AlN back-barrier will be beneficial both for good electron confinement and thermal resistance,” he adds.
“Currently, GaN-on-SiC epitaxial wafers for Ka-band applications are either immature or suffer from severe trade-offs, says SweGaN’s chief technology officer Dr Jr-Tai Chen. “Our QuanFINE epiwafers are a highly feasible solution that can resolve issues our customers are dealing with regarding short-channel effects in the high-frequency devices,” he adds. “We already have numerous product companies interested in our material as well as end users in the value chains,” continues Chen. “Four key target groups for QuanFINE epiwafers include the world’s leading foundries, IDMs (integrated device manufacturers), fabless companies, and end users, in Europe, Asia and USA.”
Key demonstrations from the joint collaboration include the following:
- physical simulations (TCAD) indicated that QuanFINE can be highly favorable for improved electron confinement;
- pulsed-IV measurements demonstrated a unique advantage of using the QuanFINE concept, showing a lower buffer-induced dispersion compared to the conventional thick, Fe-doped buffer;
- large-signal measurements demonstrate that the QuanFINE concept can provide highly competitive output power levels and efficiency, vastly beneficial to product companies and end users.
According to SweGaN, the QuanFINE concept is a thin undoped GaN channel layer in between an AlGaN barrier layer and a low-TBR (thermal boundary resistance) AlN nucleation layer that acts as a sandwich-like double heterostructure, offering sufficient two-dimensional electron gas (2DEG) confinement with much lower trapping effects compared with conventional Fe- and C-doped epi-structures. Moreover, the further reduction of GaN channel thickness will pave the way to small-gate-length device (Lg<150nm) compared with conventional AlGaN back-barrier epi-structures that suffer from weak thermal dissipation performance.
Further studies of the carbon impurity and the thickness of the unintentionally doped (UID) GaN layer are expected to further improve the ‘buffer-free’ QuanFINE concept.