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     

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     

The effect of gate recess profile on device performance ofGa0.51In0.49P/In0.2Ga0.8Asdoped-channel FET's

The effect of gate recess profile on device performance of Ga_0.51In_0.49P/In_0.2Ga_0.8As doped-channel FETs was studied. In the experiment, Ga_0.51In _0.49P/In_0.2Ga_0.8As doped-channel FETs (DCFET's) using triple-recessed gate structure were compared with devices using single-recessed and double-recessed gate structures. It is found that triple-recessed gate approach provides higher breakdown voltage (35 V) than single-recessed (16 V) and double-recessed gate (28 V) approaches. This is attributed to the larger aspect ratio in the triple-recessed gate structure. A unified method to calculate the breakdown voltages of MESFETs, HEMTs and DCFETs (or MISFETs) of any given arbitrary recessed gate profile was proposed and used to explain the experimental results     

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     

Al0.25In0.75P/Al0.48In0.52As/Ga0.35In 0.65As graded channelpseudomorphic HEMT's with high channel-breakdown voltage

A new Al_0.25In_0.75P/Al_0.48In_0.52 As/Ga_0.35In 0_.65As pseudomorphic HEMT where the InAs mole fraction of the Ga_1-xIn_xAs channel was graded (x=0.53→0.65→0.53) is described. The modification of the quantum well channel significantly improved breakdown characteristics. In addition, use of an Al_0.25In_0.75P Schottky layer increased the Schottky barrier height. Devices having 0.5 μm gate-length showed g_m of 520 mS/mm and I_max of 700 mA/mm. The gate-drain (BV_g-d) and source-drain (BV_d-s ) breakdown voltages were as high as -14 and 13 V, respectively. An f_T of 70 GHz and f_max of 90 GHz were obtained     

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     

Disordering of Ga0.47In0.53As/InP multiplequantum well layers by sulphur diffusion

The disordering of Ga_0.47In_0.53As/InP MQW layers by the diffusion of sulphur is reported for the first time. Photoluminescence measurements indicate that this results in a larger bandgap material. SIMS profiles show that intermixing of both group III and V elements occurs between wells and barriers     

Ga0.66In0.34As/GaInAsP/InP tensile-strainedsingle-quantum-well lasers with 70-nm period wire active region

Fairly low threshold current operation was achieved with Ga_0.66In_0.34As/GaInAsP/InP tensile-strained (TS) single-quantum-well (SQW) lasers with 30-~40-nm-wide and 70-nm-period wire active region fabricated by a combination of a wet chemical etching and two-step OMVPE (organometallic vapor phase epitaxy) growth. Threshold current as low as 16 mA and threshold current density of 816 A/cm² were obtained under a room temperature CW condition. In comparing the spontaneous emission peak wavelength of the TS-SQW wire laser with that of the TS-SQW film laser, an approximately 10-meV blue shift of the fundamental energy level was observed in the TS-SQW wire laser     

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     

Resonant tunnelling in Ga0.47In0.53As/InPdouble-barrier structures grown by AP-MOCVD

Reports the first observation of negative-differential resistance in Ga_0.47In_0.53As/InP double-barrier structures grown by AP-MOCVD. The devices exhibit the largest peak/valley current ratios seen in this system; 1.2:1 (2.8:1) and 3.0:1 (5.5:1) at 77 K (4.2 K) for the n=1 and n=2 resonances respectively     

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     

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     

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 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     

High performance 0.35 μm gate-length monolithicenhancement/depletion-mode metamorphicIn0.52Al0.48As/In0.53Ga0.47As HEMTs on GaAs substrates

Monolithic integration of enhancement (E)- and depletion (D)-mode metamorphic In_0.52Al_0.48As/In_0.53Ga_0.47 As/GaAs HEMTs with 0.35 μm gate-length is presented for the first time. Epilayers are grown on 3-inch SI GaAs substrates using molecular beam epitaxy. A mobility of 9550 cm²/V-s and a sheet density of 1.12×10^{12 -2} are achieved at room temperature. Buried Pt-gate was employed for E-mode devices to achieve a positive shift in the threshold voltage. Excellent characteristics are achieved with threshold voltage, maximum drain current, and extrinsic transconductance of 100 mV, 370 mA/mm and 660 mS/mm, respectively for E-mode devices, and -550 mV, 390 mA/mm and 510 mS/mm, respectively for D-mode devices. The unity current gain cutoff frequencies of 75 GHz for E-mode and 80 GHz for D-mode are reported     

Metamorphic In0.4Al0.6As/In0.4Ga0.6As HEMTs on GaAs substrate

New In_0.4Al_0.6As/In_0.4Ga_0.6 As metamorphic (MM) high electron mobility transistors (HEMTs) have been successfully fabricated on GaAs substrate with T-shaped gate lengths varying from 0.1 to 0.25 μm. The Schottky characteristics are a forward turn-on voltage of 0.7 V and a gate breakdown voltage of -10.5 V. These new MM-HEMTs exhibit typical drain currents of 600 mA/mm and extrinsic transconductance superior to 720 mS/mm. An extrinsic current cutoff frequency f_T of 195 GHz is achieved with the 0.1-μm gate length device. These results are the first reported for In_0.4 Al_0.6As/In_0.4Ga_0.6As MM-HEMTs on GaAs substrate     

High peak tunnel current densityGa0.47In0.53As Esaki diodes

High peak current density Ga_0.47In_0.53As interband tunnel diodes were fabricated by metal organic molecular beam epitaxy. A room temperature peak-to-valley current ratio of 16 and a peak tunnel current density of 9.2 kA/cm² were obtained in diodes doped to ~3×10¹⁹cm³ on both n-type and p-type sides. A peak-to-valley current ratio of 3.8, and a peak tunnel current density of 93.2 kA/cm² were obtained in diodes doped to ~10²⁰ cm^-3 on both n-type and p-type sides     

Diffusion-induced disordering ofGa0.47In0.53As/InP multiple quantum wells withzinc

Diffusing zinc into Ga_0.47In_0.53As/InP MQW layers is found to cause strong intermixing of the group III elements, which changes the composition in the quantum wells and barriers. As a result of this disordering the MQW bandgap is reduced in energy and the photoluminescence emission peak moves to longer wavelength     

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