AlN/GaN MISHEMTs on Si with in-situ SiN as gate dielectric for power amplifiers in mobile SoCs

AlN/GaN metal-insulator-semiconductor high electron mobility transistors (MISHEMTs) on silicon substrate using in-situ SiN as gate dielectric were fabricated and their RF power performance at mobile system-on-chip (SoC) compatible voltages was measured. At a mobile SoC-compatible supply voltage of Vd = 3.5 V/5 V, the 90-nm gate-length AlN/GaN MISHEMTs showed a maximum power-added efficiency (PAE) of 62%/58%, a maximum output power density (Poutmax) of 0.44 W/mm/0.84 W/mm and a linear gain of 20 dB/19 dB at the frequency of 5 GHz. These results suggest that the in-situ-SiN/AlN/GaN-on-Si MISHEMTs are promising for RF power amplifiers in 5G mobile SoC applications.

Channelized active noise elimination (CANE) for suppressing quantization noise in bitstream modulated transmitter (BMT)

Bitstream modulated transmitters may offer improved power efficiency and linearity simultaneously in RF power amplifiers. Several modulation techniques including envelop delta-sigma modulation and envelope pulse width modulation have been applied. The out-of-band quantization noise associated with these modulations may be rejected by a high-quality factor output filter, yet the in-band quantization noise needs to be further suppressed to meet the requirement of the emission mask. The proposed channelized active noise elimination technique can offer additional quantization noise suppression through software control without involving a passive filter. The essential concept is based on combining the outputs of multiple channels of Pas that have digitally controlled delays to form a FIR filter in analogue domain. A two-channel and a four-channel GaN power amplifiers are built to demonstrate this noise suppression concept and power combiners based on T-junction with quarter wavelength transmission line are proposed to retain the high power efficiency of the transmitters.

AlGaN/GaN HEMT TRAP CHARACTERISTIC FREQUENCY DEPENDENCE ON TEMPERATURE AND ITS IMPACT ON THE RF POWER AMPLIFIER LINEARIZABILITY

This paper presents a study of the linearizability of AlGaN/GaN HEMT based RF power amplifiers, RFPAs, and its relation with the active device trap activation energy. Based on the theory of thermally activated traps and on the experimental determination of the trap activation energy, we could show that despite different devices may exhibit traps with the same emission timeconstant at room temperature, their characteristic frequency may change significantly under nominal operation because of their temperature rise. And this was found to be key to explain the distinct linearizability performance of the tested devices because different stimulus dynamics excite the long-term memory effects imposed by traps with sensible different levels.