A field-effect transistor includes a carrier transport layer made of nitride semiconductor, a gate electrode having first and second sidewall surfaces on first and second sides, respectively, an insulating film formed directly on the gate electrode to cover at least one of the first and second sidewall surfaces, first and second ohmic electrodes formed on the first and second sides, respectively, a passivation film including a first portion extending from the first ohmic electrode toward the gate electrode to cover a surface area between the first ohmic electrode and the gate electrode and a second portion extending from the second ohmic electrode toward the gate electrode to cover a surface area between the second ohmic electrode and the gate electrode, wherein the insulating film is in direct contact with at least the first and second passivation film portions, and has a composition different from that of the passivation film.

Field-effect transistor

A wide variety of semiconductor devices are used in wireless power amplifiers. This paper will review the advantages and disadvantages of these devices for handheld and infrastructure applications.

RF power devices for wireless communications

The present invention relates to an integrated Doherty type amplifier arrangement and an amplifying method for such an arrangement, wherein a lumped element hybrid power divider (12) is provided for splitting input signals of main and peak amplifier stages (20, 30, 40) at predetermined phase shifts and non-equal division rates and at least one wideband lumped element artificial line (Z 1, Z2) combined with wideband compensation circuit for receiving said first amplified signal and for applying said predetermined phase shift to said first amplified signal and its higher harmonics. Thereby, the low gain of the peak amplifier is compensated by providing the non-equal power splitting at the input. Moreover, the use of the lumped element hybrid power divider leads to an improved isolation between the input ports of the main and peak amplifiers decreasing final distortions of the output signal.

Integrated doherty type amplifier arrangement with high power efficiency

A simple analytical model is proposed and shown to be effective in predicting the nonlinear behavior of single-ended amplifiers, as well as Doherty amplifiers implemented with GaAs heterojunction bipolar transistors (HBTs) for handset applications. The analytical model is based on linear and nonlinear components extracted from a vertical bipolar inter-company model for Skyworks Solutions Inc.'s InGaP/GaAs HBT devices. Equations derived from the model provide insights into effects of individual components on the gain and phase of both the single-ended and Doherty amplifiers. The model indicates that tuning the phase delay inserted in front of the auxiliary power amplifier (PA) within the Doherty can improve linearity at a high input power. The efficacy of the model is demonstrated by experimental results in which, for a Doherty PA with a tuned phase delay at the auxiliary PA side, the measured gain and phase agree with the simulation results. Furthermore, the third-order intermodulation distortion performance is improved as much as 8 dB when compared with a Doherty PA without phase delay tuning

Linearity Improvement of HBT-based Doherty Power Amplifiers Based on a Simple Analytical Model

This work shows experimental and simulated data of hot electron degradation of power AlGaAs/GaAs HFETs with different gate lengths and recess widths, and uses them to infer general indications on the bias and geometry dependence of the device high-field degradation, the meaningfulness of the breakdown voltage figure of merit from a reliability standpoint, and the physical phenomena taking place in the devices during the stress and leading to performance degradation. Possible formulations of a voltage-acceleration law for lifetime extrapolation are also tested.

Electric-field-related reliability of AlGaAs/GaAs power HFETs: bias dependence and correlation with breakdown

An L/S band high-power and low-distortion AlGaAs/GaAs heterostructure field-effect-transistor amplifier has been developed. The amplifier employed two pairs of prematched GaAs chips mounted on a single package, and the total output power was combined in a push-pull configuration with a low-loss microstrip balun circuit. The developed amplifier demonstrated state of-the-art performance of 140 W output power with 11.5 dB linear gain at 2.2 GHz. In addition, it exhibited extremely low distortion performance, which is suitable for digital cellular base station system applications.

L/S-band 140-W push-pull power AlGaAs/GaAs HFET's for digital cellular base stations

An L/S-band 240 W Doherty GaAs FET amplifier with high efficiency and low distortion has been successfully developed. The amplifier employed a simple 2-way Doherty configuration to our plastic-packaged GaAs heterojunction FETs (HJFETs). We optimized load impedance shift of the main and the peak amplifiers as a function of input power level utilizing load-pull measurement and large signal simulation. The developed Doherty amplifier demonstrated low adjacent channel leakage power ratio (ACPR) of less than -34 dBc with a power-added efficiency (PAE) of 34% at an output power (Pout) of 45 dBm with a W-CDMA signal at 2.14 GHz. It also showed 53.8 dBm saturation output power with 11.2 dB linear gain. It achieved efficiency enhancement more than 11% compared to the conventional push-pull configuration under the same ACPR conditions. To our knowledge, these represent the best results ever reported among the high power FET amplifiers for W-CDMA base stations.

A 240 W Doherty GaAs power FET amplifier with high efficiency and low distortion for W-CDMA base stations

An L/S-band high-power and low-distortion AlGaAs/GaAs HFET amplifier has been developed. The amplifier employed two pairs of pre-matched GaAs chips mounted on a single package and the total output-power was combined in push-pull configuration with a microstrip balun circuit. The developed amplifier demonstrated state-of-the-art performance of 140 W output-power with 11.5 dB linear gain at 2.2 GHz. In addition, it exhibited extremely low distortion performance, which is suitable for digital cellular base station system applications.

L/S-band 140 W push-pull power AlGaAs/GaAs HFETs for digital cellular base stations

An L/S-band highly efficient 240 W GaAs FET amplifier has been developed. The amplifier employed newly developed pseudomorphic heterojunction FETs (HJFETs) exhibiting large drain current and high gm characteristics. In addition, we employed the second harmonic tuning for the input and output matching circuit to obtain the high efficiency characteristics. The developed push-pull amplifier demonstrated 53.8-dBm (240 W) output power with 50% power added-efficiency and 12-dB linear gain at 2.12 GHz. It also showed low adjacent channel leakage power ratio (ACPR) of less than -35 dBc with a power-added efficiency of 28% at an output power of 45 dBm. The developed amplifier is suitable for digital cellular base station applications.

A 240 W power heterojunction FET with high efficiency for W-CDMA base stations

An L/S-band high-power and low-distortion GaAs FET amplifier has been developed. The amplifier employed newly developed GaAs pseudomorphic heterojunction FETs (HJFETs) exhibiting large drain current and small gm3 characteristics. In addition, the output matching circuit was designed to be in short condition for the second harmonic impedance to give the low distortion characteristics. The developed push-pull amplifier demonstrated 51.5 dBm (140 W) output-power with 13 dB linear gain at 2.2 GHz and extremely low IM3 performance of less than -40 dBc at two-tone total output-power of 43 dBm (at Vds=12 V, set Ids=4% Imax). The developed amplifier is suitable for digital cellular base station system applications.

I. Takenaka

Papers

L/S-band 140-W push-pull power AlGaAs/GaAs HFET's for digital cellular base stations

A 240 W Doherty GaAs power FET amplifier with high efficiency and low distortion for W-CDMA base stations

L/S-band 140 W push-pull power AlGaAs/GaAs HFETs for digital cellular base stations

A 240 W power heterojunction FET with high efficiency for W-CDMA base stations

Low distortion high power GaAs pseudomorphic heterojunction FETs for L/S-band digital cellular base stations