Enhancement Mode PHEMT for Single Supply High Efficiency Power Amplifiers

Abstract

An enhancement mode power PHEMT technology is demonstrated as a viable alternative to an HBT for single supply high efficiency power amplifiers. The newly developed E-PHEMT has Idss=0.5 pA/mm, Imax=190 mA/mm, Vp=+0.3 V, Gm=340 mS/mm and Vbdg=20 V. Various on-wafer loadpull results at 900 and 1800 MHz are presented. A 315 mW/mm output power with PAE=76.4% is demonstrated at 1800 MHz and 4V, while 37 mW/mm and PAE=71% is achieved at 900 MHz and 1.5V. These state of the art results for any single-supply technology were achieved by utilizing systematic harmonic loadpull measurements in conjunction with accurate large-signal modeling.

n‐Doped InGaP Nanowire Shells in GaAs/InGaP Core–Shell p–n Junctions

“…At the NW surface, depletion effects are induced by Fermi‐level pinning of surface‐states and result in a lack of free carriers, which reduce the current transporting area right at the NW surface. Therefore, the doping‐dependent surface depletion d surf is included in our modeling with a surface potential of φ s = 0.2 V for InGaP (with Equation S2, Supporting Information: d surf < 10 nm if N D = 3 · 10 18 cm −3 ) …”

Analysis of DC Characteristics and Small Signal Equivalent Circuit Parameters of GaAs Metal–Semiconductor Field Effect Transistors with Different Gate Lengths and Different Gate Contours by Two-Dimensional Device Simulations

“…Unintentional excessive undercut in gate recess etching step can change device rf power performance dramatically but has insignificant effects to the I-V curves for a short channel GaAs MESFET device. A wide recess GaAs MESFET device gives less maximum power, soft gain compression and poor linearity performance 28) when compared to a narrow recess device. This effect can be understood by the fact that surface depletion caused by the Fermi level pinning blocks current conduction for the case of a wide recess structure and thus reduces maximum rf drain current swing.…”

E-PHEMT for single supply, no drain switch, and high efficiency cellular telephone power amplifiers

“…The E-PHEMT epi structure and recess etch conditions were optimized to keep Idss at the minimal level, while maintaining Imax high enough for achieving adequate RF output power [6]. Table 1.…”

“…Enhancement-mode PHEMT (E-PHEMT) technology is gaining increased attention as a viable solution for single supply, no drain switch cellular telephone power amplifiers [1]- [6]. If Idss of E-PHEMT is kept adequately low, no drain switch is required to shut a PA off completely, wluch is attractive for component count and cost reduction of the cellular handsets.…”