Xiaomi’s GaN Low‑Voltage PA Paper Accepted at IEDM 2025

The 71st International Electron Devices Meeting (IEDM 2025) in San Francisco accepted a paper jointly authored by Xiaomi Mobile’s RF team, Suzhou Nengxun High‑Energy Semiconductor, and Hong Kong University of Science and Technology, announcing the first integration of a high‑efficiency low‑voltage silicon‑based GaN RF power‑amplifier (PA) MMIC into a mobile handset, presented in the GaN and III‑V Integration session.

Mobile communication is transitioning from 5G/5G‑Advanced to 6G, creating demands for ultra‑high efficiency, ultra‑wide bandwidth, ultra‑thin and compact RF front‑ends. Conventional GaAs power amplifiers, which have been commercial for over two decades, are approaching physical limits in electron mobility, thermal conductivity and breakdown field, making them inadequate for the higher power, lower energy consumption, and smaller form‑factor requirements of future terminals.

Wide‑bandgap GaN, with its high critical breakdown field and superior thermal conductivity, is identified as a key technology to overcome these bottlenecks. However, traditional GaN devices are designed for high‑voltage operation (28 V–48 V) and are incompatible with the low‑voltage supply architecture of smartphones, representing the primary obstacle to large‑scale mobile adoption.

To address this, the research team pursued a GaN‑on‑Si strategy, integrating circuit design with process innovation. They optimized the epitaxial structure by performing in‑situ substrate surface pretreatment and precisely controlling an AlN nucleation layer, which significantly suppressed interface reactions and crystal defects, reducing substrate‑coupling loss and buffer leakage to levels comparable with advanced SiC‑based GaN devices. A newly developed regrown ohmic‑contact process lowered the contact resistance and achieved uniform sheet resistance, thereby improving device transconductance, output power, and high‑temperature stability.

The team designed a depletion‑mode GaN HEMT with a dedicated gate‑negative‑bias architecture, incorporating precise negative‑bias and soft‑start circuitry to ensure stable switching and avoid false turn‑on or breakdown. Multi‑chip co‑design and packaging integrated the GaN HEMT PA with a Si‑CMOS power‑management chip in a high‑density module.

Experimental results show that the optimized transistor operates at a 10 V supply, achieving a power‑added efficiency (PAE) exceeding 80 % and an output‑power density of 2.84 W/mm. Compared with traditional GaAs PAs, the low‑voltage GaN PA maintains comparable linearity while delivering higher PAE and power‑level performance, representing a system‑level breakthrough.

The work validates the feasibility of low‑voltage silicon‑based GaN RF technology from device to system level and highlights its commercial potential for next‑generation high‑efficiency mobile terminals. The researchers plan to deepen collaboration with the industry chain to extend the technology to more complex communication scenarios and accelerate large‑scale commercialization.