GaN High Mobility Transistors Research Articles

Doherty power amplifier with dynamic load modulation for wireless communications

AbstractIn this article, Doherty power amplifier (DPA) with dynamic load modulation (DLM) is proposed for wireless communications with high peak‐to‐average ratio (PAR) signals. The proposed DPA with DLM operates as a conventional DPA from peak to 6‐dB back‐off powers, and DLM starts to operate at lower power than 6‐dB back‐off. The DPA with DLM was designed using 6‐W GaN high mobility transistors (HEMTs) at 1.85 GHz. The fabricated DPA with DLM shows a power‐added efficiency (PAE) of 44.7% at 10‐dB back‐off power of continuous‐wave input signal, which is 5% higher than that without DLM. Dynamic measurement was also carried out using 3.84 MHz W‐CDMA signal with 7.4 dB PAR. The measurement of the DPA with DLM exhibits an average PAE of 32.1% at output power of 27.1 dBm, and adjacent channel leakage ratio (ACLR) of −45.1 dBc, which corresponds to 6.1% improvement in PAE compared with the DPA without DLM.

Room-temperature terahertz emission from nanometer field-effect transistors

Room-temperature generation of terahertz radiation in nanometer gate length InAlAs∕InGaAs and AlGaN∕GaN high-mobility transistors is reported. A well-defined source-drain voltage threshold for the emission exists, which depends on the gate bias. Spectral analysis of the emitted radiation is presented. The highest emission power emitted from a single device reached 0.1μW.