Al/sub 0.3/Ga/sub 0.7/As/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) doped-channel field-effect transistors (DCFET's)

The properties of both lattice-matched and strained doped-channel field-effect transistors (DCFET's) have been investigated in AlGaAs/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) heterostructures with various indium mole fractions. Through electrical characterization of grown layers in conjunction with the dc and microwave device characteristics, we observed that the introduction of a 150-/spl Aring/ thick strained In/sub 0.15/Ga/sub 0.85/As channel can enhance device performance, compared to the lattice-matched one. However, a degradation of device performance was observed for larger indium mole fractions, up to x=0.25, which is associated with strain relaxation in this highly strained channel. DCFET's also preserved a more reliable performance after biased-stress testings.<>     

Avalanche noise characteristics of single Al/sub x/Ga/sub 1-x/As(0.3

Groves  C. Chia  C.K. Tozer  R.C. David  J.P.R. Rees  G.J. 《Quantum Electronics, IEEE Journal of》2005,41(1):70-75

Performance improvement in tensile-strained In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As metamorphic HEMT

This paper proposes a In/sub 0.5/Al/sub 0.5/As/In/sub x/Ga/sub 1-x/As/In/sub 0.5/Al/sub 0.5/As (x=0.3-0.5-0.3) metamorphic high-electron mobility transistor with tensile-strained channel. The tensile-strained channel structure exhibits significant improvements in dc and RF characteristics, including extrinsic transconductance, current driving capability, thermal stability, unity-gain cutoff frequency, maximum oscillation frequency, output power, power gain, and power added efficiency.     

The microwave power performance comparisons of Al/sub x/Ga/sub 1-x/As/In/sub 0.15/Ga/sub 0.85/As (x=0.3, 0.5, 0.7, 1.0) doped-channel HFETs

The properties of doped-channel field-effect transistors (DCFET) have been thoroughly investigated on Al/sub x/Ga/sub 1-x/As/InGaAs (x= 0.3, 0.5, 0.7, 1) heterostructures with various Al mole fractions. In this study, we observed that by introducing a 200-/spl Aring/-thick Al/sub 0.5/Ga/sub 0.5/As (x=0.5) Schottky layer can enhance the device power performance, as compared with the conventional x=0.3 AlGaAs composition system. However, a degradation of the device power performance was observed for further increasing the Al mole fractions owing to their high sheet resistance and surface states. Therefore, Al/sub 0.5/Ga/sub 0.5/As Schottky layer design provides a good opportunity to develop a high power device for power amplifier applications.     

Ultralow leakage In/sub 0.53/Ga/sub 0.47/As p-i-n photodetector grown on linearly graded metamorphic In/sub x/Ga/sub 1-x/P buffered GaAs substrate

A novel top-illuminated In/sub 0.53/Ga/sub 0.47/As p-i-n photodiodes (MM-PINPD) grown on GaAs substrate by using linearly graded metamorphic In/sub x/Ga/sub 1-x/P (x graded from 0.49 to 1) buffer layer is reported. The dark current, optical responsivities, noise equivalent power, and operational bandwidth of the MM-PINPD with aperture diameter of 60 /spl mu/m are 13 pA, 0.6 A/W, 3.4/spl times/10/sup -15/ W/Hz/sup 1/2/, and 7.5 GHz, respectively, at 1550 nm. The performances of the MM-PINPD on GaAs are demonstrated to be comparable to those of a similar device made on InGaAs-InP substrate.     

Double heterojunction bipolar transistor in Al/sub x/Ga/sub 1-x/As/GaAs/sub 1-y/Sb/sub y/ system

Double heterojunction bipolar transistors based on the Al/sub x/Ga/sub 1-x/As/GaAs/sub 1-y/Sb/sub y/ system are examined. The base layer consists of narrow band gap GaAs/sub 1-y/Sb/sub y/ and the emitter and collector consist of wider band gap Al/sub x/Ga/sub 1-x/As. Preliminary experimental results show that AlGaAs/GaAsSb/GaAs DHBTs exhibit a current gain of five and a maximum collector current density of 5*10/sup 4/ A/cm/sup 2/.<>     

Turn-on voltage investigation of GaAs-based bipolar transistors with Ga/sub 1-x/In/sub x/As/sub 1-y/N/sub y/ base layers

The fundamental lower limit on the turn on voltage of GaAs-based bipolar transistors is first established, then reduced with the use of a novel low energy-gap base material, Ga/sub 1-x/In/sub x/As/sub 1-y/N/sub y/. InGaP/GaInAsN DHBTs (x/spl sim/3y/spl sim/0.01) with high p-type doping levels (/spl sim/3/spl times/10/sup 19/ cm/sup -3/) and dc current gain (/spl beta//sub max//spl sim/68 at 234 /spl Omega///spl square/) are demonstrated. A reduction in the turn-on voltage over a wide range of practical base sheet resistance values (100 to 400 /spl Omega///spl square/) is established relative to both GaAs BJTs and conventional InGaP/GaAs HBTs with optimized base-emitter interfaces-over 25 mV in heavily doped, high dc current gain samples. The potential to engineer turn-on voltages comparable to Si- or InP-based bipolar devices on a GaAs platform is enabled by the use of lattice matched Ga/sub 1-x/In/sub x/As/sub 1-y/N/sub y/ alloys, which can simultaneously reduce the energy-gap and balance the lattice constant of the base layer when x/spl sim/3y.     

Negative differential resistance of GaAs/Al/sub x/Ga/sub 1-x/As multiquantum well structures under high power photoexcitation: structure optimisation for an oscillator

A study is presented of the photocurrent behaviour of p-i-n diodes having GaAs/Al/sub x/Ga/sub 1-x/As MQW absorption regions for varying incident power, incident wavelength and barrier height, given by the Al fraction x. Optimum results for applications in high power oscillators are expected to be obtained for 0.1>     

Characteristics of In/sub x/Al/sub 1-x/N-GaN high-electron mobility field-effect transistor

GaN-based field effect transistors commonly include an Al/sub x/Ga/sub 1-x/N barrier layer for confinement of a two-dimensional electron gas (2DEG) in the barrier/GaN interface. Some of the limitations of the Al/sub x/Ga/sub 1-x/N-GaN heterostructure can be, in principle, avoided by the use of In/sub x/Al/sub 1-x/N as an alternative barrier, which adds flexibility to the engineering of the polarization-induced charges by using tensile or compressive strain through varying the value of x. Here, the implementation and electrical characterization of an In/sub x/Al/sub 1-x/-GaN high electron mobility transistor with Indium content ranging from x=0.04 to x=0.15 is described. The measured 2DEG carrier concentration in the In/sub 0.04/Al/sub 0.96/N-GaN heterostructure reach 4/spl times/10/sup 13/ cm/sup -2/ at room temperature, and Hall mobility is 480 and 750 cm/sup 2//V /spl middot/ s at 300 and 10 K, respectively. The increase of Indium content in the barrier results in a shift of the transistor threshold voltage and of the peak transconductance toward positive gate values, as well as a decrease in the drain current. This is consistent with the reduction in polarization difference between GaN and In/sub x/Al/sub 1-x/N. Devices with a gate length of 0.7 /spl mu/m exhibit f/sub t/ and f/sub max/ values of 13 and 11 GHz, respectively.     

Characteristics of In/sub 0.425/Al/sub 0.575/As-InxGa/sub 1-x/As metamorphic HEMTs with pseudomorphic and symmetrically graded channels

In/sub 0.425/Al/sub 0.575/As-In/sub x/Ga/sub 1-x/As metamorphic high electron mobility transistors (MHEMTs) with two different channel designs, grown by molecular beam epitaxy (MBE) system, have been successfully investigated. Comprehensive dc and high-frequency characteristics, including the extrinsic transconductance, current driving capability, device linearity, pinch-off property, gate-voltage swing, breakdown performance, unity-gain cutoff frequency, max. oscillation frequency, output power, and power gain, etc., have been characterized and compared. In addition, complete parametric information of the small-signal device model has also been extracted and discussed for the pseudomorphic channel MHEMT (PC-MHEMT) and the V-shaped symmetrically graded channel MHEMT (SGC-MHEMT), respectively.     

10-gb/s operation of an In/sub 0.53/Ga/sub 0.47/As p-i-n photodiode on metamorphic InGaP buffered semi-insulating GaAs substrate

The SONET OC-192 receiving performance of In/sub 0.53/Ga/sub 0.47/As p-i-n photodiode grown on linearly graded metamorphic In/sub x/Ga/sub 1-x/P buffered GaAs substrate is reported. With a low-cost TO-46 package, such a device exhibits a frequency bandwidth up to 8 GHz, a bit-error rate (BER) of 10/sup -9/ at 10 Gb/s, a sensitivity of -17.8 dBm, and a noise equivalent power of 3.4/spl times/10/sup -15/ W/Hz/sup 1/2/ owing to its ultralow dark current of 3.6/spl times/10/sup -7/ A/cm/sup 2/. Eye diagram analysis at 10 Gb/s without transimpedance amplification reveals a statistically distributed Q-factor of 8.21, corresponding to a minimum BER of 1.1/spl times/10/sup -16/ at receiving power of -6 dBm.     

A novel InGaP/Al/sub x/Ga/sub 1-x/As/GaAs CEHBT

A new and interesting InGaP/Al/sub x/Ga/sub 1-x/As/GaAs composite-emitter heterojunction bipolar transistor (CEHBT) is fabricated and studied. Based on the insertion of a compositionally linear graded Al/sub x/Ga/sub 1-x/As layer, a near-continuous conduction band structure between the InGaP emitter and the GaAs base is developed. Simulation results reveal that a potential spike at the emitter/base heterointerface is completely eliminated. Experimental results show that the CEHBT exhibits good dc performances with dc current gain of 280 and greater than unity at collector current densities of J/sub C/=21kA/cm/sup 2/ and 2.70/spl times/10/sup -5/ A/cm/sup 2/, respectively. A small collector/emitter offset voltage /spl Delta/V/sub CE/ of 80 meV is also obtained. The studied CEHBT exhibits transistor action under an extremely low collector current density (2.7/spl times/10/sup -5/ A/cm/sup 2/) and useful current gains over nine decades of magnitude of collector current density. In microwave characteristics, the unity current gain cutoff frequency f/sub T/=43.2GHz and the maximum oscillation frequency f/sub max/=35.1GHz are achieved for a 3/spl times/20 /spl mu/m/sup 2/ device. Consequently, the studied device shows promise for low supply voltage and low-power circuit applications.     

High-performance, metamorphic In/sub x/Ga/sub 1-x/As tunnel diodes grown by molecular beam epitaxy

Thin In/sub x/Ga/sub 1-x/As tunnel junction diodes having compositions from x=0.53 to 0.75 that span a range of bandgap energies from 0.74 to 0.55 eV, were grown on InP and metamorphic, step-graded In/sub x/Al/sub 1-x/As/InP substrates using molecular beam epitaxy and evaluated in the context of thermophotovoltaic (TPV) applications. Both carbon and beryllium were investigated as acceptor dopants. Metamorphic tunnel diodes with a bandgap of 0.60 eV (x=0.69) using carbon acceptor doping displayed highest peak current densities, in excess of 5900 A/cm/sup 2/ at a peak voltage of 0.31 V, within a 200 /spl Aring/ total thickness tunnel junction. Identically doped lattice-matched tunnel diodes with a bandgap of 0.74 eV exhibited lower peak current densities of approximately 2200 A/cm/sup 2/ at a higher peak voltage of 0.36 V, consistent with the theoretical bandgap dependence expected for ideal tunnel diodes. Specific resistivities of the 0.60 eV bandgap devices were in the mid-10/sup -5/ /spl Omega/-cm/sup 2/ range. Together with their 200 /spl Aring/ total thickness, the electrical results make these tunnel junctions promising for TPV applications where low-resistance, thin metamorphic tunnel junctions are desired.     

Microwave performance of 0.4 mu m gate metamorphic In/sub 0.29/Al/sub 0.71/As/In/sub 0.3/Ga/sub 0.7/As HEMT on GaAs substrate

MBE grown metamorphic In/sub 0.29/Al/sub 0.71/As/In/sub 0.3/Ga/sub 0.7/As/GaAs high electron mobility transistors (HEMTs) have been successfully fabricated. A 0.4 mu m triangular gate device showed transconductance as high as 700 mS/mm at a current density of 230 mA/mm. The measured f/sub T/ was 45 GHz and f/sub max/ was 115 GHz. These high values are, to the authors knowledge, the first reported for submicrometre metamorphic InAlAs/InGaAs/GaAs HEMTs with an indium content of 30%.<>     

MESFET-like transferred-electron devices in In/sub 0.53/Ga/sub 0.47/As

In/sub 0.53/Ga/sub 0.47/As transferred-electron devices with Schottky-gate electrodes were fabricated. These devices can be used in optoelectronic circuits on InP or as millimetre wave oscillators. For the realisation of the gate electrode several enhancement layers were tested to increase the Schottky barrier height on In/sub 0.53/Ga/sub 0.47/As. The triggering of single dipole domains in the device was demonstrated.<>     

Investigation of the impact of Al mole-fraction on the consequences of RF stress on Al/sub x/Ga/sub 1-x/N/GaN MODFETs

Variations of the low-frequency noise (LFN), power, and dc characteristics of a variety of SiN/sub x/ passivated AlGaN/GaN MODFETs with different values of Al mole-fraction, gate length, and gate drain spacing upon RF stress are investigated. It is experimentally evidenced that the variation of Al mole-fraction (x) of the barrier Al/sub x/Ga/sub 1-x/N layer from 0.2 to 0.4, has no considerable impact on the drain and gate low-frequency noise current characteristics. The most noticeable variation on the device characteristics upon long-term RF stressing has been on the pinch-off voltage. Although no material degradation by increasing the Al mole-fraction has been evidenced through the low-frequency noise data, it is observed that the variation of pinch-off voltage upon RF stressing becomes more important as the Al mole-fraction increases.     

Field dependence of impact ionization coefficients in In/sub 0.53/Ga/sub 0.47/As

Electron and hole ionization coefficients in In/sub 0.53/Ga/sub 0.47/As are deduced from mixed carrier avalanche photomultiplication measurements on a series of p-i-n diode layers, eliminating other effects that can lead to an increase in photocurrent with reverse bias. Low field ionization is observed for electrons but not for holes, resulting in a larger ratio of ionization coefficients, even at moderately high electric fields than previously reported. The measured ionization coefficients are marginally lower than those of GaAs for fields above 250 kVcm/sup -1/, supporting reports of slightly higher avalanche breakdown voltages in In/sub 0.53/Ga/sub 0.47/As than in GaAs p-i-n diodes.     

Study of nickel silicide contact on Si/Si/sub 1-x/Ge/sub x/

The properties of nickel silicide formed by depositing nickel on Si/p/sup +/-Si/sub 1-x/Ge/sub x/ layer are compared with that of nickel germanosilicide on p/sup +/-Si/sub 1-x/Ge/sub x/ layer formed by depositing Ni directly on p/sup +/-Si/sub 1-x/Ge/sub x/ layer without silicon consuming layer. After thermal annealing, nickel silicide on Si/p/sup +/-Si/sub 1-x/Ge/sub x/ layer shows lower sheet resistance and specific contact resistivity than that of nickel germanosilicide on p/sup +/-Si/sub 1-x/Ge/sub x/ layer. In addition, small junction leakage current is also observed for nickel silicide on a Si/p/sup +/-Si/sub 1-x/Ge/sub x//n-Si diode. In summary, with a Si consuming layer on top of the Si/sub 1-x/Ge/sub x/, the nickel silicide contact formed demonstrated improved electrical and materials characteristics as compared with the nickel germanosilicide contact which was formed directly on the Si/sub 1-x/Ge/sub x/ layer.     

Submicron-gate ion-implanted In/sub 0.15/Ga/sub 0.85/As/GaAs MESFETs with graded indium composition

0.25 mu m and 0.5 mu m gate ion-implanted MESFETs have been fabricated on In/sub 0.15/Ga/sub 0.85/As epitaxial layers. These layers are grown by MOCVD on three inch diameter GaAs substrates with the indium mole fraction graded from 15% at the InGaAs/GaAs heterointerface to 0% at the surface. Both devices show excellent DC and microwave performance. From S-parameter measurements, extrinsic current gain cutoff frequencies f/sub t/ of 120 and 61 GHz are obtained for the 0.25 mu m and 0.5 mu m gate MESFETs, respectively. The authors investigate the potential of small-bandgap InGaAs materials for submicron-gate MESFET applications.<>     

Optical tuning of monolithic In/sub 0.53/Ga/sub 0.47/As/In/sub 0.52/Al/sub 0.48/As/InP modulation-doped field-effect transistor oscillators at X and R band

The authors have experimentally studied the optical control and optical tuning characteristics of monolithically integrated In/sub 0.53/Ga/sub 0.47/As/In/sub 0.52/Al/sub 0.48/As modulation-doped field-effect transistor (MODFET) oscillators operating in the X and R bands. For a 20 mu W intrinsic photoexcitation on the device, the maximum frequency shift for the X- and R-band oscillators was 8.7 and 11.7 MHz, respectively.<>