Self-alignedIn0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistors with graded interface onsemi-insulating InP grown by molecular beam epitaxy

A self aligned In_0.52Al_0.48As/In_0.53 Ga_0.47As double heterojunction bipolar transistor (HBT) with a graded heterointerface has been grown by molecular-beam epitaxy (MBE) and tested. The DC characteristics of HBT structures with a compositionally graded junction using a linear graded In_0.53Ga_0.47-xAl_xAs between two ternary layers were investigated. Typical quaternary graded devices with an emitter dimension of 50×50 μm² exhibited a current gain as high as 1260, as compared to 800 for abrupt devices, at a collector current density of 2.8×10³ A/cm²     

In0.52Al0.48As/In0.53Ga0.47As double-heterojunction p-n-p bipolar transistors grown bymolecular beam epitaxy

P-n-p In_0.52Al_0.48As/In_0.53Ga_0.47 As double-heterojunction bipolar transistors with a p⁺-InAs emitter cap layer grown by molecular-beam epitaxy have been realized and tested. A five-period 15-Å-thick In_0.53Ga_0.47As/InAs superlattice was incorporated between the In_0.53Ga_0.47As and InAs cap layer to smooth out the valence-band discontinuity. Specific contact resistance of 1×10^-5 and 2×10^-6 Ω-cm² were measured for nonalloyed emitter and base contacts, respectively. A maximum common emitter current gain of 70 has been measured for a 1500-Å-thick base transistor at a collector current density of 1.2×10³ A/cm². Typical current gains of devices with 50×50-μm² emitter areas were around 50 with ideality factors of 1.4     

Quantum-well Hall devices in Si-delta-dopedAl0.25Ga0.75As/GaAs and pseudomorphic Al0.25Ga0.75As/In0.25Ga0.75As/GaAsheterostructures grown by LP-MOCVD: performance comparisons

Characterized herein are quantum-well Hall devices in Si-delta-doped Al_0.25Ga_0.75As/GaAs and pseudomorphic Al_0.25Ga_0.75As/In_0.25Ga _0.75As/GaAs heterostructures, grown by low-pressure metal organic chemical vapor deposition method. The Si-delta-doping technique has been applied to quantum-well Hall devices for the first time. As a result high electron mobilities of 8100 cm^-2/V·s with a sheet electron density of 1.5×10¹² cm^-2 in Al_0.25Ga_0.75As/In_0.25Ga_0.75 As/GaAs structure and of 6000 cm^-2/V·s with the sheet electron density of 1.2×10¹² cm^-2 in Al_0.25Ga_0.75As/GaAs structure have been achieved at room temperature, respectively. From Hall devices in Al_0.25Ga_0.75As/In_0.25Ga_0.75 As structure, the product sensitivity of 420 V/AT with temperature coefficient of -0.015 %/K has been obtained. This temperature characteristic is one of the best result reported. Additionally, a high signal-to-noise ratio corresponding to the minimum detectable magnetic field of 45 nT at 1 kHz and 75 nT at 100 Hz has been attained. These resolutions are among the best reported results     

In0.52Al0.48As/InAs/InxAl1-xAs pseudomorphic HEMT's on InP

The DC and microwave performance of an InAs channel HEMT is reported. Room-temperature electron mobility as high as 20200 cm² /Vs is measured, with a high carrier concentration of 2.7×10 ¹² cm^-2. DC extrinsic transconductance of 714 mS/mm is measured and a unity-current-gain cut-off frequency of 50 GHz is obtained for a 1.1-μm gate length HEMT. The success of achieving superior Hall mobility and device performance is strongly dependent on the In_xAl_1-xAs buffer layer design that changes the lattice constant from lattice-matched In_0.52Al_0.48 As to In_0.75Al_0.25As. The multiple In_0.52Al_0.48As/InAs monolayer superlattices buffer achieves the best performance as compared to the step-graded In_x Al_1-xAs and the uniform In_0.76Al_0.25 As buffer     

Electron transport in 0.15-μm gate In0.52Al0.48As/In0.53Ga0.47As HEMT

Magneto-transport and cyclotron resonance measurements were made to determine directly the density, mobility, and the effective mass of the charge carriers in a high-performance 0.15-μm gate In_0.52 Al_0.48As/In_0.53Ga_0.47As high-electron-mobility transistor (HEMT) at low temperatures. At the gate voltage V_G=0 V, the carrier density n _g under the gate is 9×10¹¹ cm^-2, while outside of the gate region n_g=2.1×10¹² cm^-2. The mobility under the gate at 4.2 K is as low as 400 cm²/V-s when V_G<0.1 V and rapidly approaches 11000 cm²/V-s when V_G>0.1 V. The existence of this high mobility threshold is crucial to the operation of the device and sets its high-performance region in V_G>0.1 V     

Characteristics of strained In0.65Ga0.35As/In0.52Al0.48As HEMT withoptimized transport parameters

The DC and microwave performance of a strained In₀.₆₅Ga₀.₃₅As/In₀ .₅₂A1₀.₄₈As HEMT (high-electron-mobility transistors) is reported. Its design is based on theoretical and experimental studies including low- and high-field transport characterization of heterostructures with different strains. The intrinsic DC transconductance and cutoff frequence of 1.4-μm-long gate HEMTs are 574 mS/mm and 38.6 GHz, respectively. The increased indium (In) composition in the channel enhances the drift velocity from 1.35×10⁷ to 1.55×10⁷ cm/s at 300 K     

Improved strained HEMT characteristics using double-heterojunctionIn0.65Ga0.35As/In0.52Al0.48As design

The DC and microwave properties of strained In_0.65Ga _0.35As/In₀₅₂Al_0.48As HEMTs (high electron-mobility transistors) with double-heterojunction design are presented. The high sheet carrier density and good carrier confinement give rise to excellent device performance with very low output conductance. For 1×150-μm² long-gate HEMTs, the measured cutoff frequency f_T and maximum frequency of oscillation f_max are as high as 37 and 66 GHz, respectively     

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     

Low temperature microwave characteristics of 0.1 μm gate-lengthpseudomorphicIn0.52Al0.48As/InxGa1-xAs(x=0.85 and 0.95) MODFET's

We have studied the microwave characteristics of 0.1 μm gate-length pseudomorphic In_0.52Al_0.48As/In_x Ga_1-xAs (x=0.85 and 0.95) modulation-doped field-effect transistors (MODFET's) at 300 K and lower temperatures down to 77 K. A maximum f_T of 151 GHz has been measured for a 0.1×55 μm² gate In_0.52Al_0.48As/In_0.85 Ga_0.15As MODFET at 77 K and this represents an improvement of 33% over the room temperature value. This behavior has been analyzed     

Self-aligned InAlAs/InGaAs heterojunction bipolar transistor with aburied subcollector grown by selective epitaxy

We report the first microwave characterization of an In_0.52 Al_0.48As/In_0.53Ga_0.47As heterojunction bipolar transistor (HBT) with a buried InGaAs subcollector grown by selective epitaxy. The study compares two HBT's having identical 2×10 μm² self-aligned emitter fingers but different subcollectors. Improvement in microwave performance of the selectively-grown HBT over the conventional HBT was observed due to the reduced parasitic base-collector capacitance achieved by incorporating the selectively-grown buried subcollector     

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     

DC and RF performance of LP-MOCVD grownAl0.25Ga0.75As/InxGa1-xAs(x=0.15-0.28) P-HEMT's with Si-delta doped GaAs layer

Si-delta-doped Al_0.25Ga_0.75As/In_xGa_1-xAs (x=0.15-0.28) P-HEMT's, prepared by LP-MOCVD, are investigated. The large conduction band discontinuity leads to 2-DEG density as high as 2.1×10¹²/cm² with an electron mobility of 7300 cm²/V·s at 300 K. The P-HEMT's with 0.7×60 μm gate have a maximum extrinsic transconductance of 380 mS/mm, and a maximum current density of 300 mA/mm. The S-parameter measurements indicate that the current gain and power gain cutoff frequencies are 30 and 61 GHz, respectively, The RF noise characteristics exhibit a minimum noise figure of 1.2 dB with an associated gain of 10 dB at 10 GHz. Due to the efficient doping technique, the electron mobility and transconductance obtained are among the best reported for MOCVD grown P-HEMT's with the similar structure     

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     

Performance of In0.53Ga0.47As and InPjunction field-effect transistors for optoelectronic integratedcircuits. I. Device analysis

The authors have developed an analytical model to study In_0.53Ga_0.47As and InP junction field-effect transistors (JFETs) for use in InP-based optoelectronic integrated circuits (OEICs). This model includes the effects of channel resistance and band-to-band tunneling. The agreement between the calculations and experimental results supports the validity of the model. The authors discuss the optimum design for these JFETs and compare their performance quantitatively. In order to prevent device performance from being degraded by the effects of tunneling, the optimum channel dopings of In _0.53Ga_0.47As and InP JFETs are found to be 7×10¹⁶ and 5×10¹⁷ cm^-3, respectively. In_0.53Ga_0.47As JFETs not operated in the tunneling regime show at least a 40% higher efficiency than InP JFETs in terms of the power dissipated per transconductance. The authors conclude that In_0.53Ga_0.47As JFETs are well suited for very-high-density monolithic integration, where power efficiency must be high     

Picosecond-switching time ofIn0.53Ga0.47As/AlAs resonant-tunneling diodesmeasured by electro-optic sampling technique

To demonstrate picosecond-switching time for In_0.53Ga _0.47As/AlAs resonant-tunneling diodes (RTD's), we fabricated RTD's with various barrier widths and measured their switching times using electro-optic sampling technique specially arranged for RTD's with high current density. For an RTD having the barrier width of 1.4 nm with the peak current density of 4.5×10⁵ A/cm² and peak-to-valley ratio of 3.9, the switching time of 2.2 ps has been observed     

Fabrication of high-performance AlxGa1-xAs/InyGa1-yAs/GaAs resonant tunneling diodes using amicrowave-compatible technology

A microwave-compatible process for fabricating planar integrated resonant tunneling diodes (RTDs) is described. High-performance RTDs have been fabricated using Al_xGa_1-xAs/In_y Ga_1-yAs/GaAs strained layers. Peak-to-valley current ratios (PVRs) of 4.8:1 with simultaneous peak current densities of 4×10⁴ A/cm² have been achieved at room temperature for diodes of area 9 μm². Accurate measurements of reflection gain versus frequency between 1.5 and 26.5 GHz in the negative differential region indicate that the present technology is promising for millimeter-wave integrated circuits including self-oscillating mixers, frequency multipliers, and detectors     

Fabrication of 0.15-μm Γ-Shaped Gate In0.52Al0.48As/In0.6Ga0.4As Metamorphic HEMTs Using DUV Lithography and Tilt Dry-Etching Technique

An In_0.52Al_0.48As/In_0.6Ga_0.4 As metamorphic high-electron mobility transistor (MHEMT) with 0.15-mum Gamma-shaped gate using deep ultraviolet lithography and tilt dry-etching technique is demonstrated. The developed submicrometer gate technology is simple and of low cost as compared to the conventional E-beam lithography or other hybrid techniques. The gate length is controllable by adjusting the tilt angle during the dry-etching process. The fabricated 0.15-mum In_0.52Al_0.48As/In_0.6Ga_0.4As MHEMT using this novel technique shows a saturated drain-source current of 680 mA/mm and a transconductance of 728 mS/mm. The f_T and f_max of the MHEMT are 130 and 180 GHz, respectively. The developed technique is a promising low-cost alternative to the conventional submicrometer E-beam gate technology used for the fabrication for GaAs MHEMTs and monolithic microwave integrated circuits     

High-quality two-dimensional electron gas inAlxGa1-xAs/GaAs heterostructures by LP-OMVPE

A combination of high mobility and high sheet carrier density in Al_xGa_1-xAs/GaAs two-dimensional electron gas (2DEG) elements was obtained by low-pressure organometallic vapor phase epitaxy (OMVPE). The sheet charge densities (n_s) and mobilities (μ) at 77 K are 1.2×10¹²/cm² and 90000 cm²/V-s for single-channel, and 2.0× 10¹²/cm² and 64500 cm²/V-s for double-channel elements, respectively. Strong correlations between the photoluminescence spectrum of the Al_xGa_1-xAs layers and the 2DEG mobility were found. The 2DEG elements were used as mixers and detectors at millimeter wavelengths. Mixing at 94 GHz with a 1.7-GHz IF bandwidth and detection of signals as high as 238 GHz under a magnetic field were achieved with these devices     

Long-wavelength In0.53Ga0.47As metamorphicp-i-n photodiodes on GaAs substrates

Metamorphic In_0.53Ga_0.47As p-i-n photodiodes on GaAs substrate exhibiting the lowest dark current ever reported were fabricated and characterized. Their dark current, DC and RF performances were measured and compared for devices of different sizes. Typical dark current for 15-μm-diameter devices was 600 pA under 5-V reverse bias, corresponding to a dark current density of 3.40×10^-4 A/cm². Typical responsivity measured with 1.55-μm optical radiation was 0.55 A/W corresponding to an external quantum efficiency of 44%. The electrical 3 dB bandwidths of the photodiodes with diameters smaller than 20 μm were over 20 GHz     

Doubly strainedIn0.41Al0.59As/n+-In0.65Ga0.35As HFET with high breakdown voltage

An In_0.41Al_0.59As/n⁺-In_0.65 Ga_0.35As HFET on InP was designed and fabricated, using the following methodology to enhance device breakdown: a quantum-well channel to introduce electron quantization and increase the effective channel bandgap, a strained In_0.41Al_0.59As insulator, and the elimination of parasitic mesa-sidewall gate leakage. The In_0.65Ga_0.35As channel is optimally doped to N_D=6×10¹⁸ cm^-3. The resulting device (L_g=1.9 μm, W_g =200 μm) has f_t=14.9 GHz, f_max in the range of 85 to 101 GHz, MSG=17.6 dB at 12 GHz V_B=12.8 V, and I_D(max)=302 mA/mm. This structure offers the promise of high-voltage applications at high frequencies on InP