Compatibility issues of Si technology with higher band gap materials for RF applications (original) (raw)
Related papers
2011
The effects of recess etch in alloyed ohmic contacts have been studied on InAl(Ga)N/AlN/GaN high-electron-mobility transistors (HEMTs) using a Si-containing ohmic metal stack. The optimized contact resistance is as low as 0.23 mm. With decent ohmic contacts, an In 0:13 Al 0:83 Ga 0:04 N barrier HEMT with a 66-nm long gate and dielectric-free passivation followed by a 5 nm Al 2 O 3 deposition, shows a maximum drain current density I d,max of 2.3 A/mm, a peak extrinsic transconductance g m,ext of 560 mS/mm and a current gain cutoff frequency f T of 210 GHz, which are among the highest reported values in quaternary InAlGaN/AlN/GaN HEMTs.
IEEE Transactions on Electron Devices, 2000
The dc, small-signal microwave, and large-signal switching performance of normally off and normally on Alo.sGao.sAs gate heterojunction GaAs field-effect transistors (HJFET) with submicrometer gate lengths are reported. The structure of both types of devices comprises an n-type 1017-cm-3 Sn-doped active layer on a Cr-doped GaAs substrate, a p-type 1018-cm-3 Ge-doped Alo.SGao.SAs gate layer and a p+-type 5 X 1018-cm-3 Ge-doped GaAs "contact and cap" layer on the top of the gate. The gate structure is obtained by selectively etching the p+-type GaAs and Alo.sGao.sAs. Undercutting oftheAlo.sGao.sAs layer results in submicrometer gate lengths, and the resulting p+-GaAs overhang is used to self-align the source and the drain with ~TEpect to the gate. Normally off GaAs FET's with 0.5-to 0.7-pm long heterbjunction gates exhibit maximum available power gains (MAG) of about
IEEE Transactions on Electron Devices, 1989
A theoretical and experimental study of step-doped HEMT's with light and heavy doped regions is presented. Threshold voltage control and sensitivity with respect to growth parameters and recess etching, and design criteria are investigated for these structures. A three-regime charge control model is used to predict their performance. Using the same semi-analytical theory, which was validated with the help of a self-consistent analysis, both conventional and step-doped HEMT's with an i-layer are compared. 1-pm gate-length n-channel HEMT's with step-doped profile thicknesses of 25,50, and 100 A were fabricated and tested at low and high frequencies. The low-frequency noise can be controlled by the step thickness, and a noise analysis is presented. Cutoff frequencies of 16 to 18 GHz and maximum oscillation frequencies of 41 to 59 GHz were measured and correlated to the step thickness.
Large transconductance n+Ge gate AlGaAs/GaAs MISFET with thin gate insulator
IEEE Electron Device Letters, 1986
The effects of insulator layer thickness on an n+-Ge gate MISFET were studied. The transconductance increases with decreasing AlGaAs layer thickness from 60 down to 10 nm. From the variation of the intrinsic transconductance, the effective insulator layer thickness was found to be enlarged by'about 9 nm. This is due to the finite width of twodimensional electron gas (2-DEG). A large transconductance of 430 mS/ mm was obtained at room temperature for the 0.8-pm gate-length FET with 10-nm-thick AIGaAs. This large transconductance demonstrates the inherent potential of the n +-Ge gate MISFET for LSI application.
Silicon, 2019
In this paper an Underlap Double Gate (U-DG) Symmetric Heterojunction AlGaN/GaN Metal Oxide Semiconductor High Electron Mobility Transistor (MOS-HEMT) with gate oxide materials of different dielectric constant has been studied using gate oxide materials such as Hafnium dioxide (HfO 2), Silicon dioxide (SiO 2) and a symmetric gate stack (GS) of HfO 2-SiO 2. In this work, the analog performance of the devices has been studied on the basis of parameters like transconductance (g m), transconductance generation factor (g m /I D) and intrinsic gain (g m R 0). This paper depicts the effect of varying oxide materials on the analog and RF figure of merits (FOMs) such as the gate to drain capacitance (C GD), gate to source capacitance (C GS) and total gate capacitance (C GG), intrinsic resistances, cutoff frequency (f T) and maximum frequency of oscillation (f MAX) using nonquasi-static approach. Studies show that the introduction of a gate oxide layer in the MOS-HEMT device increases the gate controllability reducing gate leakage currents improving RF performance. U-DG AlGaN/GaN MOS-HEMT with HfO 2 gate dielectric shows superior Power output efficiency (POE) of 55% compared to the HfO 2-SiO 2 composite structure and SiO 2 with 26% and 20% respectively.
2017
AlGaN/GaN/Si HEMTs grown by molecular beam epitaxy are studied with several means of characterization, the most used are direct-current and radio-frequency measurements, to see power and microwave performance of components. As has been found, the maximum of drain current achieves 0,4 A and 3,54 10 21 cm -3 of 2DEG carrier concentration. Device simulation was also carried on in ATLAS to probe into the operation mechanism of GaN HEMTs and demonstrate those result. As we used this last simulation tool to extract the Radio-frequency parameter; cut-off frequency (Ft), maximum oscillation frequency (Fmax), variation maximum stable gain (Gms) and maximum available gain (Gma), consequently we will know the microwave power performance and area component application.
IEEE Transactions on Electron Devices, 2010
The linearity of conventional pseudomorphic AlGaAs/InGaAs/AlGaAs high-electron mobility transistors with planar doping in the AlGaAs layers is shown to degrade at low temperatures down to −40 • C, as measured by the adjacentchannel power ratio under wideband code-division multipleaccess modulation. A modified structure, in which the planar Si doping layers are placed within thin single GaAs quantum wells inside the AlGaAs barrier layers, eliminates this degradation. Deep-level transient spectroscopy and persistent photocapacitance measurements show that trapping on DX centers is effectively eliminated. The linearity improvements are therefore attributed to the elimination of this trapping. Self-consistent solutions of the Schrödinger and Poisson equations show that the transfer of the donor electrons into the channel is essentially the same in the modified and conventional structures. Index Terms-Deep-level transient spectroscopy (DLTS), deep levels, DX centers, linearity, modulation-doped field-effect transistors (MODFETs), quantum-well devices. I. INTRODUCTION P SEUDOMORPHIC HEMT (pHEMT) devices incorporating n-doped AlGaAs barriers and coherently strained InGaAs quantum-well channel regions [1], [2] exhibit desirable characteristics in RF applications, such as high transconductance, high operating frequencies, low noise figures, high power-added efficiencies, and high output powers [2]. They have therefore found wide application in power amplifiers for base stations at frequencies of 3.5 GHz and above, where the competing Si lateral double-diffused metal-oxidesemiconductor (LDMOS) technology begins to become efficiency limited [3], [4].
Materials Research Society eBooks, 2003
Recent advances in the AlGaN/GaN-based HEMTs grown on thermally conductive SiC substrates have demonstrated the strong potential of this technology for the next-generation microwave p o wer applications, especially near X-band (8-12 GHz). Power density o f greater than 10 W/mm was demonstrated at 10 GHz by Cornell group, which w as 8 times greater than GaAs-based state-of-the-art devices. Microwave p o wer operations beyond the X-band toward mm-wave h a ve received a great deal of attention. Utilizing 0.15 um gate-length passivated AlGaN/GaN HEMTs grown on semi-insulating (0001) 4H-SiC substrates using RF-assisted MBE, we h a ve reported CW output power density of 6.6 W/mm with PAE of 35% at 20 GHz from 0.1 mm devices. At Ka-band, CW output power densities ranging 1.5 2.3 W/mm have been reported with PAE ranging 26% (pulsed) 22% by several groups. The power density is at least 3 times greater than that of GaAs pHEMTs. Thus, the observed superior power performance indicates its strong potential toward mm-wave p o wer ampliers. The PAE, however, is very much lacking for the real system insertion, which might be due to both lower linear gain and high knee voltage under the CW high RF power operation. Further improvement in PAE is expected in the gate-recessed devices. Recently, w e h a ve reported gate-recessed AlGaN/GaN HEMTs, where the gate area was dry etched using a chlorine-based low p o wer RIE. The 0.85 um gate-recessed devices showed Ids of 0.5 A/mm with knee voltage of 3 V. The small signal RF measurement showed the maximum oscillation frequency (fmax) and unity-gain cut-o frequency (fT) of 44 GHz, and 15 GHz, respectively. Submicron gate recessed AlGaN/GaN HEMTs were also fabricated down to 0.15 um gate length. We observed a systematic reduction both in threshold voltage and Idss, and an improvement in transconductance. For instance, we observed extrinsic transconductance of 350 mS/mm from 0.3 um gate recessed devices with Vt =-0.8 V. Preliminary testing of 0.15 um gate recessed devices with Vt of-4 V and knee voltage of 3 V , s h o wed extrinsic ft of 67 GHz and fmax of 120 GHz. Power performance of recessed gate AlGaN/GaN HEMTs at mm-wave frequencies will be presented and compared with non-recessed AlGaN/GaN HEMTs.