Ga0.51In0.49P/In0.15Ga0.85As/GaAs pseudomorphic doped-channel FET with high-current densityand high-breakdown voltage

Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs pseudomorphic doped-channel FETs exhibiting excellent DC and microwave characteristics were successfully fabricated. A high peak transconductance of 350 mS/mm, a high gate-drain breakdown voltage of 31 V and a high maximum current density (575 mA/mm) were achieved. These results demonstrate that high transconductance and high breakdown voltage could be attained by using In_0.15Ga_0.85As and Ga_0.51In_0.49P as the channel and insulator materials, respectively. We also measured a high-current gain cut-off frequency f_t of 23.3 GHz and a high maximum oscillation frequency f_max of 50.8 GHz for a 1-μm gate length device at 300 K. RF values where higher than those of other works of InGaAs channel pseudomorphic doped-channel FETs (DCFETs), high electron mobility transistors (HEMTs), and heterostructure FETs (HFETs) with the same gate length and were mainly attributed to higher transconductance due to higher mobility, while the DC values were comparable with the other works. The above results suggested that Ga_0.51In_0.49P/In_0.15Ga_0.85 As/GaAs doped channel FET's were were very suitable for microwave high power device application     

Enhancement mode metamorphicAl0.67In0.33As/Ga0.66In0.34As HEMT on GaAs substrate with high breakdown voltage

This paper presents original and experimental results provided by E-mode Al_0.67In_0.33As/Ga_0.66In_0.34 As metamorphic HEMT. The devices exhibit good dc and rf performances. The 0.4 μm gate length devices have saturation current density of 355 mA/mm at +0.6 V gate-to-source voltage. The Schottky characteristic is a typical reverse gate-to-drain breakdown voltage of -16 V. It is the first time, to our knowledge, that gate current issued from impact ionization have been observed in these devices versus gate to drain extension. These results are the first reported for E-mode Al _0.67In_0.33As/Ga_0.66In_0.34As MM-HEMTs on GaAs substrate     

InP-based HEMT's with Al0.48In0.52AsxP1-x Schottky layers

In this letter we report on the DC and RF performance of InP-based HEMT's with Al_0.48In_0.52As_xP_1-x Schottky layers and GaInAs/InP composite channels. By replacing the Al_0.48In_0.52As Schottky layer with Al_0.48 In_0.52As_xP_1-x we have been able to increase the bandgap of the Schottky layer and achieve record breakdown voltages for 0.15 μm gate-length InP-based HEMT's. The 0.15 μm gate-length HEMT's have gate-to-drain breakdown voltages of over 13 V with current densities of 620 mA/mm and maximum transconductances of 730 mS/mm. On a wafer with a higher sheet charge we have obtained gate-to-drain breakdown voltages of 10.5 V with current densities of over 900 mA/mm. These are the highest breakdown voltages reported for 0.15 μm gate-length InP-based HEMT's with such high current densities. At 10 GHz a 450 μm wide HEMT has demonstrated 350 mW (780 mW/mm) of output power with power-added efficiency of 60% and 12 dB gain     

High-linearity high-current-drivabilityGa0.51In0.49P/GaAs MISFET usingGa0.51In0.49P airbridge gate structure grown byGSMBE

A novel structure Ga_0.51In_0.49P/GaAs MISFET with an undoped Ga_0.51In_0.49P layer serving as the airbridge between active region and gate pad was first designed and fabricated. Wide and flat characteristics of g_m and f_max versus drain current or gate voltage were achieved. The device also showed a very high maximum current density (610 mA/mm) and a very high gate-to-drain breakdown voltage (25 V). Parasitic capacitances and leakage currents were minimized by the airbridge gate structure and thus high f_T of 22 GHz and high f_max of 40 GHz for 1 μm gate length devices were attained. To our knowledge, both were the best reported values for 1 μm gate GaAs channel FET's     

25.5% efficient Ga0.35In0.65P/Ga0.83In0.17As tandem solar cells grown on GaAs substrates

Theoretical calculations predict a higher power conversion efficiency for the combination of Ga_0.35In_0.65P and Ga_0.83In_0.17As in a tandem solar cell, compared to the more commonly used Ga_0.51In_0.49P/GaAs approach. A record conversion efficiency of 21.6% (AM1.5 g) was recently achieved for a 1.18 eV Ga_0.83In_0.17As solar cell, grown lattice-mismatched to the GaAs substrate material. This paper reports on the device characteristics of first Ga_0.35In_0.65P/Ga_0.83In_0.17As tandem solar cells based on this very promising GaInAs material. A high quantum efficiency, comparable to the lattice-matched Ga_0.51In_0.49P on GaAs approach was achieved. A power conversion efficiency of 25.5% was measured under AM1.5d spectral conditions     

High-breakdown-voltage Ga0.51In0.49P channelMESFET's grown by GSMBE

The first Ga_0.51In_0.49P channel MESFETs grown on a (100) GaAs substrate by GSMBE have been fabricated. A high gate-to-drain breakdown voltage of 42 V with a high maximum current density (320 mA/mm) was achieved. This result demonstrates that high-breakdown voltage could be attained by using Ga_0.51In _0.49P as the channel material. We also measured a high-maximum oscillation frequency (f_max) of 30 GHz for a 1.5 μm gate-length device. This value is quite high compared with other high-breakdown-voltage GaAs MESFET's or MISFET's with the same gate length     

A 0.15-μm 60-GHz high-power composite channel GaInAs/InP HEMTwith low gate current

This letter presents recent improvements and experimental results provided by GaInAs/InP composite channel high electron mobility transistors (HEMT). The devices exhibit good dc and rf performance. The 0.15-μm gate length devices have saturation current density of 750 mA/mm at V_GS=+0 V. The Schottky characteristic is a typical reverse gate-to-drain breakdown voltage of -8 V. Gate current issued from impact ionization has been studied in these devices, in the first instance, versus drain extension. At 60 GHz, an output power of 385 mW/mm has been obtained in such a device with a 5.3 dB linear gain and 41% drain efficiency which constitutes the state-of-the-art. These results studied are the first reported for a composite channel Al_0.65In_0.35As/Ga_0.47In_0.53 As/InP HEMT on an InP substrate     

Enhancement-mode Al0.66In0.34As/Ga0.67In0.33As metamorphic HEMT, modeling and measurements

This paper exhibits experimental and theoretical results on metamorphic high-electron mobility transistor (MM-HEMT). Modeling and measurements provide a better knowledge of device physics which allows us to optimize device structures. We present 10-GHz power performances, pulse and gate measurements, and two-dimensional (2-D) hydrodynamic modeling of enhancement-mode (E-mode) Al_0.66In_0.34As/Ga_0.67In_0.33 As NM-HEMT devices. It is the first time that cap layer thickness has been studied for a MM-HEMT. A typical reverse breakdown voltage of 16 V has been obtained. Gate current issued from impact ionization has been shown, for the first time, in such a device. The 2-D hydrodynamic model is a useful tool for cost engineering because it brings more information in terms of physical quantity distributions, necessary to predict breakdown behavior of FET. The 10-GHz measurements with a load-pull power set-up demonstrate the capabilities for a thick cap device with large gate-to-drain extension since an output power of 140 mW/mm have been obtained which is the state-of-the-art for such a device. These results obtained confirm the great interest of the structures for power application systems. The only work reported, to our knowledge, using a MM-HEMT structure in E-mode with an indium content close to 50% has been studied by Eisenbeiser et al.. Their typical gate-to-drain breakdown voltage was 5.2 V. The 0.6 μm ×3 mm devices exhibited 30 mW/mm at 850 MHz     

Schottky barrier heights of n-type and p-type Al0.48In0.52As

The authors report electrical measurements on four different metal contacts which formed Schottky barriers to lightly doped complementary n- and p-type Al_0.48In_0.52As epitaxial material grown by molecular beam epitaxy on semi-insulating InP substrates. The Schottky contact metals studied were Au, Al, Pt, and tri-layer Ti/Pt/Au. The Schottky barrier heights varied from 0.560 eV for Al on n-type AlInAs to 0.905 eV for Al on p-type AlInAs, with intermediate values for the other metals studied. The sum of n- and p-type Schottky barrier heights for each metal contact ranged from 1.440 to 1.465 eV, in good agreement with the accepted Al_0.48In_0.52As bandgap value of 1.45 eV     

High-performance Ga0.51In0.49P/GaAs airbridgegate MISFET's grown by gas-source MBE

Ga_0.51In_0.49P/GaAs MISFET's, in which Ga_0.51In_0.49P insulating layer was inserted between the gate metal and the channel layer, were compared with MESFET's experimentally and theoretically in terms of DC and microwave performance. Devices performance were evaluated by varying the thickness of the insulating layer. Wide and flat characteristics of g_m, g_t, and f_max versus drain current (or gate voltage) together with a high maximum current density (above 610 mA/mm) were achieved for devices with insulating layer thickness of 50 mn and 100 mm. Moreover, the maximum values of J_t's and f_max 's for a 1-μm gate length device both occurred when t was between 50 and 100 mn. We also observed that parasitic capacitances and gate leakage currents were minimized by using the airbridge gate structure, and thus high-frequency and breakdown characteristics were greatly improved, These results demonstrate that Ga_0.51In_0.49P/GaAs airbridge gate MISFET's with insulating layer thickness between 50 and 100 mn were very suitable for microwave high-power device applications     

High-performance highly strainedGa0.23In0.77As/Al0.48In0.52As MODFET's obtained by selective and shallow etch guide recesstechniques

Record high f_TL_g products of 57 and 46 GHz-μm have been achieved in Ga_1-x In_x As/AlInAs MODFETs with a strain compensated channel of x=0.77 and a lattice-matched channel of x=0.53, respectively. Although g_m as high as 950 mS/mm has been obtained by conventional deep recess for the gate, these latter devices show a prominent kink effect which lowers f_T and the voltage gain. By limiting the depth of final nonselective recess etch to 3 nm with the help of selective step etches, f_T as high as 47 GHz and g_m as high as 843 mS/mm have been achieved for MODFETs with x=0.77 and L_g=1.1 μm     

Single- and double-heterojunction pseudomorphic In0.5(Al0.3Ga0.7)0.5P/In0.2Ga0.8As high electron mobility transistors grown by gas sourcemolecular beam epitaxy

In_0.5(Al_0.3Ga_0.7)_0.5 P/In_0.2Ga_0.8As single- and double-heterojunction pseudomorphic high electron mobility transistors (SH-PHEMTs and DH-PHEMTs) on GaAs grown by gas-source molecular beam epitaxy (GSMBE) were demonstrated for the first time. SH-PHEMTs with a 1-μm gate-length showed a peak extrinsic transconductance g_m of 293 mS/mm and a full channel current density I_max of 350 mA/mm. The corresponding values of g_m and I_max were 320 mS/mm and 550 mA/mm, respectively, for the DH-PHEMTs. A short-circuit current gain (H₂₁) cutoff frequency f_T of 21 GHz and a maximum oscillation frequency f_max of 64 GHz were obtained from a 1 μm DH device. The improved device performance is attributed to the large ΔE_c provided by the In_0.5(Al_0.3Ga_0.7)_0.5P/In _0.2Ga_0.8As heterojunctions. These results demonstrated that In_0.5(Al_0.3Ga_0.7)_0.5P/In _0.2Ga_0.8As PHEMT's are promising candidates for microwave power applications     

High-transconductance heterostructure Ga0.47In0.53As/InP metal-insulator-semiconductor field-effect transistorsgrown by chemical beam epitaxy

SiO₂ insulator is on top of an InP layer; current transport occurs, however, an in adjacent n-type Ga_0.47In_0.53As:Sn layer. A transconductance of g_m=300 mS/mm is obtained from depletion-mode MISFETs with a gate length of 1.2 μm. This MIS (metal-insulator-semiconductor) junction has a symmetric current-voltage characteristic and a low-leakage current of ~1 nA at ±2 V. High-frequency S-parameter measurements performed b probing devices on the wafers yield a unity current gain frequency of F _t=22.2 GHz and a maximum frequency of oscillation f _max=27 GHz     

0.2-μm gate-length atomic-planar doped pseudomorphic Al0.3Ga0.7As/In0.25Ga0.75As MODFETswith fT over 120 GHz

The authors report the DC and RF performance of nominally 0.2-μm-gate length atomic-planar doped pseudomorphic Al_0.3Ga_0.7As/In_0.25Ga_0.75As modulation-doped field-effect transistors (MODFETs) with f_T over 120 GHz. The devices exhibit a maximum two-dimensional electron gas (2 DEG) sheet density of 2.4×10¹² cm^-2, peak transconductance g _m of 530-570 mS/mm. maximum current density of 500-550 mA/mm, and peak current-gain cutoff frequency f_T of 110-122 GHz. These results are claimed to be among the best ever reported for pseudomorphic AlGaAs/InGaAs MODFETs and are attributed to the high 2 DEG sheet density, rather than an enhanced saturation velocity, in the In_0.25Ga_0.75As channel     

Ga0.47In0.53As depletion mode MISFETs withnegligible drain current drift

Ga_0.47In_0.53As depletion-mode metal insulator semiconductor field-effect transistors with a transconductance in the range 100-140 mS/mm and with no significant current drift (less than 3% in 30 hours) have been fabricated on epitaxial layers grown by MOCVD. This high performance has been achieved using an efficient passivation of the GaInAs surface which associates in situ native oxide removal by a hydrogen multipolar plasma and a Si₃N₄ film deposition     

Incorporation behaviour of carbon and silicon on (100) and (111) surfaces during growth of GaAs/GaAs and Ga0.47In0.53As/InP by molecular beam epitaxy

Silicon and carbontetrabromide were used as dopant sources in the growth of GaAs/GaAs and Ga_0.47In_0.53As/InP structures. We studied the incorporation behaviour of these group IV atoms on (100) and {111} surfaces as a function of growth temperature. The free carver concentrations determined by Hall measurements for Si-doped GaAs and Ga_0.47In_0.53As layers are independent of growth temperature on all surface orientations studied. Silicon acts fundamentally as a donor except, as expected, for doped layers on (111)A GaAs substrates, where it acts as an acceptor. Carbon incorporation in GaAs and Ga_0.47In_0.53As always results in a p-type conduction independent of the surface orientations (100)/{111} or the growth temperatures we used. In contrast to the results on GaAs, carbon shows a strong temperature-dependent activation in Ga_0.47In_0.53As grown on (100) and (111)B surfaces. Carbon-doped Ga_0.47In_0.53As on (111)A and carbon-doped GaAs layers on (100)/{111} GaAs surfaces exhibit only a very weak dependence of the carrier concentration on the growth temperature. A significant amphoteric behaviour of carbon was not observed in any of the materials investigated.     

Ga0.47In0.53As metal-semiconductor-metalphotodiodes using a lattice mismatchedAl0.4Ga0.6As Schottky assist layer

Metal-semiconductor-metal photodiodes (MSM PDs) with Ga_0.47 In_0.53As active layers were fabricated. The low Schottky barrier height of GaInAs was overcome by the insertion of a lattice mismatched AlGaAs intermediary layer between metal and GaInAs active layer. Fabricated MSM PDs utilising interdigitated metal electrodes formed by a self-alignment technique showed a fast rise and fall time of 650 ps, which was limited by the capacitance of the device. The gain of the device was less than 1     

Characteristics of short-wavelength (617<λ<640 nm) Ga0.4In0.6P/(AlxGa1-x)0.5In0.5P strained, thin multiple-quantum-well lasers

The authors examine the operating characteristics of short wavelength (617<λ<640 nm) AlGaInP lasers containing three thin (~20 Å) compressively strained Ga_0.4In_0.6 P/(Al_0.6Ga_0.4)_0.5In_0.5 P quantum wells and Al_0.5In_0.5P cladding layers, grown by low pressure organometallic vapor phase epitaxy. At room temperature, wavelengths as short as 617 nm have been achieved, with pulsed threshold current density of 2.5 kA/cm². As a result of greater electron confinement at longer wavelengths, the threshold, and its temperature sensitivity, are improved     

Graded pseudomorphic channel AlInP/AlInAs/GaInAs HEMTs with highchannel breakdown voltage

Reports effects of the composition grading of the channel on the device characteristics of Al_0.48In_0.52As/Ga_1-xIn_xAs pseudomorphic HEMTs. Systematic studies reveal that the modification of the quantum-well channel by grading the composition considerably changes the channel breakdown (BV_ds) and output conductance (G₀ ) characteristics. HEMTs with graded Ga_1-xIn_xAs channel (from x=0.7 to x=0.6) exhibited significantly improved BV_ds (11V) and g₀ (40 mS/mm) compared with HEMTs with uniform composition (x=0.7) in the channel (BV_ds=4V and g₀=80 mS/mm)     

High-frequency submicrometerAl0.48In0.52As/In0.53Ga0.47As heterostructure bipolar transistors

The high speed scaling of an Al_0.48In_0.52As/In_0.53Ga_0.47 As submicrometer heterostructure bipolar transistor (HBT) is presented. Transistors with emitter dimensions of 0.5×11 and 3.5×3.5 μm² exhibit unity current-gain cutoff frequencies of 63 and 70 GHz, respectively. Emitter current density greater than 3.3×10⁵ A/cm² is demonstrated in a submicrometer AlInAs/InGaAs HBT. The analysis shows that the device speed is limited by the parasitic collector charging time