Jae Kyoung Mun

2.9 V operation GaAs power MESFET with 31.5-dBm output power and 64% power-added efficiency

A state-of-the-art GaAs power MESFET operating at a drain bias of 2.9 V has been developed using the high-low doped channel structure grown by molecular beam epitaxy. The device has 0.6 /spl mu/m gate length and 16 mm gate width. The power performance tested at a 2.9 V drain bias and 900 MHz operation frequency was output power of 31.5 dBm with 11.5 dB gain and 64% power-added efficiency. >

A 68% PAE, GaAs power MESFET operating at 2.3 V drain bias for low distortion power applications

A high-efficient GaAs power metal semiconductor field effect transistor operating at a drain voltage of 2.3 V has been developed for low distortion power applications. The device has been fabricated on an epitaxial layer with a high-low doped structure grown by molecular beam epitaxy. The MESFET with a gate length of 0.8 /spl mu/m and a total gate width of 21.16 mm showed a maximum drain current of 5.9 A at V/sub gs/=0.5 V, a knee voltage of 1.0 V and a gate-to-drain breakdown voltage of 28 V. The MESFET tested at a 2.3 V drain bias and a 900 MHz operation frequency displayed the best power-added efficiency of 68% with an output power of 31.3 dBm. The associate power gain at 20 dBm input power and the linear gain were 11.3 dB and 16.0 dB, respectively. The power characteristics of the device operating under a bias of 2 V exhibit power-added efficiency of 67% and output power of 30.1 dBm at an input power of 20 dBm. Two tone test measured at 900.00 MHz and 900.03 MHz shows that 3rd-order intermodulation and power-added efficiency at an output power of 27 dBm were -30.6 dBc and 36%, respectively, which are good for CDMA digital applications. A third-order intercept point and a linearity figure-of-merit were measured to be 49.5 dBm and 53.8, respectively.

Pd/Ge/Ti/Au ohmic contact to AlGaAs/InGaAs pseudomorphic high electron mobility transistor with an undoped cap layer

The Pd/Ge/Ti/Au ohmic contact to AlGaAs/InGaAs pseudomorphic high electron mobility transistor was investigated with the etch depth of an undoped GaAs/AlGaAs cap layer. The contact resistivity decreases from 9.5×10−5 to 2.3×10−6u2009Ωu2009cm2 when the contacts were formed on a n-Al0.23Ga0.77As layer by removing the undoped cap layer. X-ray diffraction results show that the good ohmic contact is due to the formation of Au2Al as well as β-AuGa. Both compounds play a role to create group-III vacancies, followed by the incorporation of Ge into group-III vacancies, namely, creation of free electron below the contact. This results in the considerable elimination of contact resistivity by lowering the effective tunneling barrier.

Thermal degradation mechanism of Ti/Pt/Au Schottky contact to n-type GaAs

The thermal stability of Ti/Pt/Au Schottky gates on high-low doped GaAs metal–semiconductor field-effect transistors (MESFETs) was investigated in the temperature range of 300–500u2009°C, using current–voltage and capacitance–voltage measurements and cross-sectional transmission electron microscopy with energy dispersive x-ray spectroscopy. At annealing temperatures >350u2009°C, the interfacial reactions cause the formation of a layered structure of Ti/Ti–Ga/Ti–As/GaAs. The depth distribution of electron concentration moves toward the Ti/GaAs interface as the annealing temperature increases. This is due to the growth of Ti–As, followed by the reduction of the channel thickness. The activation energy for the growth of Ti–As is determined to be 1.74 eV. The electron concentration in the channel layer decreases with the increase of the annealing temperature. This is due to the out-diffusion of Ga to the Ti film, resulting in the production of acceptor-type Ga vacancies and thereby the decrease of electron concentrat...

Electrical characteristics of metal–insulator–semiconductor Schottky diodes using a photowashing treatment in AlxGa1−xAs/InGaAs (X=0.75) pseudomorphic high electron mobility transistors

Metal–insulator–semiconductor (MIS) Schottky diodes on Al0.75Ga0.25As/In0.2Ga0.8As pseudomorphic high electron mobility transistors were produced using both photowashing and H2O2 treatments. The Schottky contact on a GaAs layer showed enhancement of the Schottky barrier height of 0.11 eV for the photowashing and 0.05 eV for the H2O2 treatment, respectively. After the photowashing treatment, the Ga oxide (Ga2O3) was dominantly created. In the meanwhile, two types of As oxide (As2O3,As5O2) were mainly produced by the H2O2 treatment, which were distributed uniformly over the GaAs surface. At the same oxide thickness, the formation of the Ga oxide after the photowashing treatment is more effective in enhancement of the Schottky barrier height. This is due to the fact that the Ga oxide was more favorable in the creation of a fixed interface state density, which is known as an origin for increase of the barrier height, compared to the As oxide in the GaAs MIS Schottky diode.

A Ku-band T-shaped gate GaAs power MESFET with high breakdown voltage for satellite communications

/sup G/aAs power MESFETs with 0.5-/spl mu/m T-shaped gate for Ku-band power applications have been developed using a new self-aligned and optical lithography. It displays a maximum current density of 350 mA/mm, an uniform transconductance of 150 mS/mm and a high gate-to-drain breakdown voltage of 35 V. Both the high breakdown voltage and the uniform transconductance were achieved by the new MESFET design incorporating an undoped GaAs cap and a thick lightly doped active layers. The breakdown voltage is the highest one among the values reported on the power devices. The device exhibits 0.61 W/mm power density and 47% power added efficiency with 9.0 dB associated gain at a drain bias of 12 V and an operation frequency of 12 GHz.

2.3 V operation GaAs power MESFET with 68% power-added efficiency

A state-of-the-art GaAs power MESFET operating at a drain bias of 2.3 V has been developed using the low-high doped channel structure. The device has 0.8-/spl mu/m gate length and 21-mm gate width. The power performance tested at a 2.3 V drain bias under 900 MHz operation frequency was output power of 31.3-dBm with 11.3-dB gain and 69-percent power-added efficiency. A third-order intercept point was evaluated to be 50.7-dBm. A Linearity Figure-of-Merit of 55.6 was recorded for 21-mm-wide FET.

Effects of photowashing treatment on electrical properties of a GaAs metal–semiconductor field-effect transistor

Effects of photowashing treatment on electrical properties of GaAs metal–semiconductor field-effect transistors (MESFETs) were investigated using x-ray photoemission spectroscopy. The binding energy of the Ga–As bond shifted toward lower binding energies and the ratio of Ga/As was increased, namely the formation of the Ga-rich surface. This suggests that acceptor-type defects GaAs− were produced by the photowashing treatment and the level for Fermi energy pinning at the surface moved to acceptor states. The Fermi energy pinning caused by GaAs− results in an increase of the depletion layer width at the ungated region of the MESFET via the increase of band bending from the surface. Therefore the drain current density at a positive gate bias and the leakage current at gate-to-drain were simultaneously reduced.

Degradation mechanism of GaAs MESFETs

Abstract The reliability of the Au/Pt/Ti Schottky gate of low–high doped GaAs MESFETs has been investigated by thermal step stress and accelerated life tests and their degradation mechanisms were analyzed by means of Auger electron spectroscopy, X-ray diffractometry, cross-sectional transmission electron microscopy, current–voltage, and capacitance–voltage measurements. Electrical measurements showed that the failure of the GaAs MESFETs was mainly due to the degradation of the Au/Pt/Ti/GaAs Schottky contact. An activation energy of 1.3xa0eV and a lifetime of 2×108xa0h at 125°C for Schottky contact were evaluated. At a temperature lower than 350°C, the degradation of the Schottky contact is attributed to the decrease of net electron concentration caused by outdiffusion of host Ga atoms of GaAs. The activation energy for the decrease of net electron concentration is determined to be 1.4xa0eV using the capacitance–voltage measurement, which is consistent with 1.3xa0eV obtained by the accelerated life tests. This suggests that the major thermal degradation mechanism at a temperature lower than 350°C is the outdiffusion of Ga atoms from the channel. Meanwhile, the effective channel thickness at a temperature higher than 350°C is reduced by the formation of TiAs at the Schottky interface, the activation energy of which is determined to be 1.74xa0eV.

Failure analysis for RF characteristics of GaAs MESFETs

Abstract The effect of thermal stress on the noise degradation of GaAs MESFETs was investigated. Minimum noise figure, associated gain, scattering parameters, and capacitance–voltage profiles were measured during the tests, and the electro-chemical properties after thermal stress were analyzed by means of Auger electron spectroscopy, X-ray diffractometery, cross-sectional transmission electron microscopy, and capacitance–voltage measurements. The RF failure mode consists of an increase of the minimum noise figure and a decrease of associated gain of the FETs. The extracted equivalent circuit elements from measured scattering parameters were used to evaluate the influence of each parameter on the noise degradation. The parametric estimation showed that the noise degradation was mainly attributed to the decrease of a.c. transconductance. From the C – V analysis, we found that the decrease of a.c. transconductance was caused by the decrease of effective carrier concentration. From the electro-chemical analysis, the decrease in effective carrier concentration was resulted from the gate-sinking by the thermally activated interdiffusion between the gate metal and the GaAs channel layer. Therefore, the thermally activated carrier compensation by Ga vacancies in the channel is proposed to be the main failure mechanism for noise degradation of GaAs MESFETs.