R. Kaliski

Millimeter-wave ion-implanted graded In/sub x/Ga/sub 1-x/As MESFETs grown by MOCVD

The authors present the fabrication and characterization of ion-implanted graded In/sub x/Ga/sub 1-x/As/GaAs MESFETs. The In/sub x/Ga/sub 1-x/As layers are grown on GaAs substrates by MOCVD (metal-organic chemical vapor deposition) with InAs concentration graded from 15% at the substrate to 0% at the surface. 0.5- mu m gate MESFETs are fabricated on these wafers using silicon ion implantation. In addition to improved Schottky contact, the graded In/sub x/Ga/sub 1-x/As MESFET achieves maximum extrinsic transconductance of 460 mS/mm and a current-gain cutoff frequency f/sub t/ of 61 GHz, which is the highest ever reported for a 0.5- mu m gate MESFET. In comparison, In/sub 0.1/Ga/sub 0.9/As MESFETs fabricated with the same processing technique show an f/sub t/ of 55 GHz.<<ETX>>

Full functionality of LSI gate arrays fabricated on 3-in-diameter, MOCVD-grown GaAs-on-silicon substrates

Fully functional, 504-gate arrays have been fabricated on an MOCVD (metalorganic chemical-vapor deposition)-grown, 3-in-diameter, GaAs-on-silicon substrate. Each ECL (emitter-coupled-logic)-compatible gate array consists of an eight-bit adder, a D flip-flop, a 214 divider (with a divide-by-four tap), and a 263-stage inverter string. These circuits represent 90% gate utilization, or approximately 6600 transistors. The wafer-level yield of fully functional gate arrays is 10.7%. This demonstrates total functionality and yield for a digital circuit with LSI-level complexity using MOCVD-grown GaAs-on-silicon material and shows that this material, even with defect densities greater than 108 cm/sup -2/, is viable for high-density LSI circuits.<<ETX>>

Heteroepitaxial In0.1Ga0.9As metal‐semiconductor field‐effect transistors fabricated on GaAs and Si substrates

We present a comparison of device characteristics for In0.1 Ga0.9 As metal‐semiconductor field‐effect transistors (MESFETs) fabricated on GaAs and silicon substrates. The In0.1Ga0.9As layers are heteroepitaxially grown on GaAs and silicon substrates by metalorganic chemical vapor deposition. 0.5 μm gate devices fabricated on the GaAs substrate show a maximum extrinsic transconductance of 450 mS/mm and a current‐gain cutoff frequency ft of 55 GHz. Despite the large lattice mismatch, the In0.1 Ga0.9 As MESFETs fabricated on the silicon substrate show a comparable ft of 52 GHz with a lower gain.

Ion-implanted In0.1Ga0.9As metal-semiconductor field-effect transistors on GaAs (100) substrates

Ion‐implanted In0.1Ga0.9As metal‐semiconductor field‐effect transistors (MESFETs) have been fabricated on 3 in. GaAs (100) substrates. The structure comprises an undoped InGaAs epitaxially layer grown directly on a GaAs (100) substrate by the metalorganic chemical vapor deposition (MOCVD) technique. Si+28 is ion implanted into the InGaAs layer to form an active channel layer. MESFETs with 100 μm gate width and 0.5 μm gate length are fabricated using standard process techniques. The best device shows a maximum transconductance of 426 mS/mm. From S‐parameter measurements, the current‐gain cutoff frequency ft is 37 GHz and the maximum available gain cutoff frequency fmax is 85 GHz. These results are comparable to InGaAs MESFETs grown by MBE.

Graded heterojunction ion-implanted FETs: a combination of heteroepitaxy and ion implantation

FETs fabricated by ion implantation into inverted GaAs-AlGaAs heterostructures grown by MOCVD are discussed. The AlAs fraction in the AlGaAs layer is graded from 0% at the substrate to 30% at the heterointerface. 0.5- mu m gate devices fabricated with the graded heterojunction show two transconductance peaks that are both greater than 420 mS/mm. These devices also exhibit enhanced power gain, especially at low drain current, when compared with conventional ion-implanted GaAs MESFETs. The f/sub t/ of the graded heterojunction device is relatively insensitive to the gate bias. At 20% of I/sub dss/, the measured extrinsic f/sub t/ is 40 GHz, which increases slightly up to 47 and 41 GHz at 50 and 100% of I/sub dss/, respectively. Electron accumulation at the graded GaAs-AlGaAs heterointerface leads to improve device performance at low current bias. >

Misfit In0.18Ga0.82As/GaAs metal‐semiconductor field‐effect transistors with improved Schottky gate characteristics

In0.18Ga0.82As epitaxial layers having a thickness much greater than the established critical thickness of pseudomorphic layers have been grown on GaAs substrates. 0.25 μm gate metal‐semiconductor field‐effect transistors (MESFETs) are fabricated by silicon ion implantation into the epitaxial wafers. In spite of the large lattice mismatch and the high defect density, the devices show excellent device performance with a maximum extrinsic transconductance of 620 mS/mm and a current‐gain cutoff frequency fT of 92.8 GHz. Furthermore, the Schottky gate characteristics of this device are shown to be comparable to those of GaAs MESFETs.

Highly lattice-mismatched In/sub 0.26/Ga/sub 0.74/As/GaAs MESFET's: impact of critical thickness on device performance

Fabrication of 0.25- mu m-gate MESFETs directly on In/sub 0.26/Ga/sub 0.74/As epitaxial layers which are much thicker than the pseudomorphic critical thickness is described. The InAs mole fraction is increased in the MESFET channel to 26%. Whether the device performance can be further improved without detrimental dislocation effects as the channel thickness exceeds the critical thickness considerably is investigated. Despite large lattice mismatch and high defect density, these devices show excellent microwave performance with an extrinsic f/sub t/ of 120 GHz. Bias-dependent S-parameters indicate that the In/sub 0.26/Ga/sub 0.74/As MESFET maintains excellent device performance down to very low drain current without showing any performance degradation due to misfit or threading dislocations.<<ETX>>

Ion-implanted GaAs/AlGaAs heterojunction FET's grown by MOCVD

The successful fabrication of an ion-implanted GaAs/AlGaAs heterojunction FET device is discussed. Half-micrometer gate-length FET devices are fabricated by ion implantation into GaAs/AlGa heterostructures grown by metalorganic chemical vapor deposition (MOCVD) on 3-in-diameter GaAs substrates. The FET device exhibits a maximum extrinsic transconductance of 280 mS/mm with reduced transconductance variation over 2 V of gate bias. Excellent microwave performance is achieved with an f/sub t/ of 40 GHz, which is comparable to results obtained from 0.25- mu m gate GaAs MESFETs. The effects of ion implantation on the heterojunction and corresponding device characteristics are also discussed.<<ETX>>

Mixed technology of ion implantation and heteroepitaxy: ion-implanted In/sub x/Ga/sub 1-x/As/GaAs MESFETs

State-of-the-art FET performance with f/sub t/s of 55 and 61 GHz has been achieved using 0.5- mu m-gate In/sub 0.1/Ga/sub 0.9/As and graded In/sub x/Ga/sub 1-x/As MESFETs, respectively. The material growth and device fabrication are described, and the device characteristics are reported. In comparison to the In/sub 0.1/Ga/sub 0.9/As MESFET, the graded-material MESFET shows a better Schottky gate, which is essential for device performance. This novel InGaAs MESFET is of interest for InGaAs-based circuits that are suitable, among other applications, for long-wavelength fiber-optic communication.<<ETX>>

Heterojunction ion-implanted FETs (HIFETs)

Summary form only given. The authors report the enhanced microwave performance of ion-implanted MESFETs fabricated on graded GaAs-AlGaAs heterostructures. Since low-noise MESFETs are typically biased at a low drain current, optimum low-noise operation requires high f/sub 1/ at low drain currents. f/sub t/ values reported in the literature are generally measured close to I/sub dss/. This 0.5- mu m gate heterojunction ion-implanted FET (HIFET) exhibits enhanced microwave performance, especially at low drain current, when compared to conventional ion-implanted GaAs MESFETs. At 20% of I/sub dss/, the current gain cutoff frequency f/sub t/ is 40 GHz, which increases to 47 GHz at 50% of I/sub dss/. At 100% of I/sub dss/, the f/sub t/ is 41 GHz. The maximum stable gain at 25 GHz of the HIFET is also 4 dB higher than that of the conventional MESFET. >