A high power density 26 V GaAs pHEMT technology

Abstract

Abseacs This report presents a GaAs pHEMT technology optimized for 26 V drain bias. At this bias, a 2.14 GHz gate width scaling study demonstrates output power densities of 1.8-2.1 Wlmm of output power at 1 dB gain compression Qlm) for device sum ranging from 14.4 mm down to 3.6 mm respectively. Power added efficiency (PAE) remains nearly constant at 59-61% for these device sues. Devices with 14.4 mm gate widths produced a PI^ of 26 W (1.8 W / m ) with an associated power-added efficiency (PAE) of 61%. Thermal imaging shows a thermal resistance of approximately 4.2 "CIW at a 36 OC case temperature for 14.4 mm (26 W) device. A high temperature step stress reliability study shows a median t h e to failure (MTTF) of 1.6 X IO' hours for a 150 'C channel temperature with a thermal activation energy of 1.8 eV. These results represent the hest combination of power density, PAE, and reliability reported for any GaAs-based FET technology.

GaN- and SiC-Based Power Devices

“…Take the example of the GaAs-based FETs; a high-output power density of 1.4 W mm À1 at 8 GHz was reported back in 1981 (Macksey and Doerbeck, 1998). Recent elaborated GaAs FETs with electric field mitigation and state-of-the art processes surpassed 2.1 W mm À1 at 2-3 GHz in 2004 (Green et al, 2004) and reached 3.6 W mm À1 in 2007 (Fanning et al, 2007). The improvement is not very significant considering the much lower operation frequency.…”

Design, performance and application of high voltage GaAs FETs

“…However, high channel current results in reduced offstate breakdown unless the transistor is designed properly. Breakdown improvements have been made through the use of a field-modulating plate in close proximity to the gate Schottky contact as well as using wide band gap materials, such as InGaP, for the channel layer [1][2][3][4][5]. Design tradeoffs between the device geometry and channel layer definition have to be made.…”

“…The reduction in gain is a direct result of an increase in total gate capacitance. Figure 2 illustrates a comparison of |H21| and MSG/MAG for the two field plate structures in a 26V pHEMT technology [4]. In practical terms a device with field plate connected to ground offers a power gain increase over step gate device of 3-5 dB.…”

Ultra-Broadband GaAs HIFET MMIC PA

“…While connecting devices DC in series helps in biasing at higher voltages, the RF impedance of the RF parallel combination becomes very low, leading to difficulties in matching for broadband applications. Recently, there have been reports [3][4][5][6] of high DC bias voltage operation from FET, PHEMT, SiC and GaN devices. But theses devices are either very expensive or still in the R&D stage with immature technology.…”