High-performance InAlAs/InGaAs HEMTs and MESFETs

The fabrication and microwave performance of heterostructure InAlAs/InGaAs HEMTs (high-electron-mobility transistors) and MESFETs are described. Maximum stable gains of 14.3 dB for a HEMT and 12 dB for a MESFET at 26.5 GHz have been achieved. These are believed to be record gains for FETs having gates as long as 0.7 μm     

High-performance double-modulation-doped InAlAs/InGaAs/InAs HFETs

We demonstrate the improvement of double-sided-doped InAlAs/InGaAs MODFETs by inserting a thin InAs layer in the center of the conventional InGaAs channel. A maximum extrinsic transconductance of 1.4 S/mm is achieved for 0.13-μm devices. The current gain cutoff frequency of this device is as high as 265 GHz. Delay time analysis shows a significant improvement in the effective saturated velocity, from 2.4×10⁷ cm/s for LM devices to 3.1×10⁷ cm/s for InAs devices. We believe the superior performance of this device is primarily due to the reduction of scattering from donor layers, especially under the channel, and the interface roughness, which is achieved by inserting a 4-nm InAs layer in the channel     

Impact ionization in InAlAs/InGaAs/InAlAs HEMT's

The kink effect and excess gate current in InAlAs/InGaAs/InAlAs HEMT's have been linked to impact ionization in the high field region of the channel. In this letter, a relationship is established between experimentally measured excess gate current and the tunneling of holes from the quantum well formed in the channel. The channel hole current is then obtained as the quotient of the excess gate current to the gate-voltage-dependent transmission probability. This channel hole current follows the exponential dependence of the ionization constant on the inverse electric field     

Design, fabrication, and performance of high-speed monolithicallyintegrated InAlAs/InGaAs/InP MSM/HEMT photoreceivers

A detailed study of the performance of monolithically integrated photoreceivers based on metal-semiconductor-metal (MSM) photodetectors (PD's) and HEMT's is undertaken. Two different stacked-layer approaches to integrating MSM-PD's with HEMT's are investigated, and the performance of detectors and HEMT's for each approach is compared. The structure with the MSM layers grown on top of the HEMT layers exhibited the best overall performance. A physics-based MSM model is developed and incorporated into microwave circuit design software; excellent agreement between circuit simulations and measured frequency responses is demonstrated. To evaluate the effects of MSM electrode geometry and detector area on photoreceiver performance, photoreceivers with MSM interelectrode spacings of 1, 1.5, and 2 μm were fabricated and characterized. The electrical amplifier used in the photoreceivers is a two-stage, variable-transimpedance amplifier with a common-gate HEMT as the feedback path. By adjusting the DC voltage applied to the gate of this feedback HEMT, transimpedances ranging from 55.8 to 38.1 dBΩ, with corresponding -3 dB cutoff frequencies from 6.3 to 18.5 GHz, were measured experimentally. Excellent noise performance has been measured, with average input noise current spectral densities of 7.5, 8, and 12 pA/Hz^1/2 obtained for bandwidths of 6.3, 8, and 13.7 GHz, respectively. A packaged receiver has been tested at 5 Gb/s and an open eye pattern obtained     

High-performance, 0.1 μm InAlAs/InGaAs high electron mobilitytransistors on GaAs

This letter describes the material characterization and device test of InAlAs/InGaAs high electron mobility transistors (HEMTs) grown on GaAs substrates with indium compositions and performance comparable to InP-based devices. This technology demonstrates the potential for lowered production cost of very high performance devices. The transistors were fabricated from material with room temperature channel electron mobilities and carrier concentrations of μ=10000 cm² /Vs, n=3.2×10¹² cm^-2 (In=53%) and μ=11800 cm²/Vs, n=2.8×10¹² cm^-2 (In=60%). A series of In=53%, 0.1×100 μm² and 0.1×50 μm² devices demonstrated extrinsic transconductance values greater than 1 S/mm with the best device reaching 1.074 S/mm. High-frequency testing of 0.1×50 μm² discrete HEMT's up to 40 GHz and fitting of a small signal equivalent circuit yielded an intrinsic transconductance (g_m,i) of 1.67 S/mm, with unity current gain frequency (f_T) of 150 GHz and a maximum frequency of oscillation (f_max) of 330 GHz. Transistors with In=60% exhibited an extrinsic g_m of 1.7 S/mm, which is the highest reported value for a GaAs based device     

Delta-doping-enhanced InGaAs/InAlAs heterobarrier diodes

Modification of the effective conduction-band offset in InGaAs/InAlAs isotype heterojunctions by incorporating, during epitaxial growth, a doping dipole formed by alternate n⁺, p⁺ delta (δ-) doping is demonstrated. Greatly improved current rectification is found when the dipole polarity enhances the potential barrier     

Ordering in InGaAs/InAlAs layers

The structure of InCaAs/InAlAs layers lattice matched to an InP substrate, grown on either (100) or on (110) with a 4° tilt toward [111] at 500 and 300°C has been investigated by transmission electron microscopy. High perfection resulted for the layers grown on [001] oriented substrates whereas growth on the near [110] substrates resulted in compositional nonuniformities, macrosteps formation, and ordering of the group III elements. This difference in structural perfection between the two sets of samples was also reflected in differences in electrical properties.     

A novel InAlAs/InGaAs two-terminal real-space transfer diode

We report a two-terminal real-space transfer diode (RSTD) using a InAlAs/InGaAs heterojunction grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). By virtue of nonalloyed ohmic contacts as well as a sewer layer which is electrically separated from ohmic electrodes, a carrier density modulation and a strong negative differential resistance can be obtained. A peak-to-valley current ratio up to 140000 (1×10⁶) at 300 (77) K are, to our knowledge, among the best for InAlAs/InGaAs structures. The proposed device also reveals sharp charge injection and broad valley range     

Impact ionization in InAlAs/InGaAs HFET's

The presence of an energy barrier to the transfer of holes from the channel to the gate electrode of InAlAs/InGaAs HFET's prevents the gate current from being a reliable indicator of impact ionization. Consequently, we have used a specially designed sidegate structure to demonstrate that due to the narrow bandgap of InGaAs, impact ionization takes place in the channel of these devices under normal operating conditions. The ionization coefficient was found to follow a classic exponential dependence on the inverse electric field at the drain end of the gate, for over three orders of magnitude     

应变补偿InGaAs/InAlAs量子级联激光器

利用应变补偿的方法研制出激射波长 λ≈ 3.5— 3.7μm的量子级联激光器 .条宽 2 0 μm,腔长 1 .6mm的 Inx Ga1- x As/Iny Al1- y As量子级联激光器已实现室温准连续激射 .在最大输出功率处的准连续激射可持续 30 min以上 .     

High-speed InAlAs/InGaAs heterojunction bipolar transistors

InAlAs/InGaAs heterojunction bipolar transistors fabricated from wafers grown by molecular beam epitaxy are discussed. A cutoff frequency of 32 GHz for a collector current of 20 mA is achieved in the emitter area of devices 6×10 μm². The use of heavily doped and nondoped InGaAs layers as the emitter cap and collector, respectively, results in a reduction of the emitter and collector charging times; this, in turn, leads to improved microwave performance     

应变补偿InGaAs/InAlAs量子级联激光器

利用应变补偿的方法研制出激射波长λ≈3.5—3.7μm的量子级联激光器.条宽20μm,腔长1.6mm的InxGa1-xAs/InyAl1-yAs量子级联激光器已实现室温准连续激射.在最大输出功率处的准连续激射可持续30min以上.     

InAlAs/InGaAs HBT X-band double-balanced upconverter

We report on an InAlAs/InGaAs HBT Gilbert cell double-balanced mixer which upconverts a 3 GHz IF signal to an RF frequency of 5-12 GHz. The mixer cell achieves a conversion loss of between 0.8 dB and 2.6 dB from 5 to 12 GHz. The LO-RF and IF-RF isolations are better than 30 dB at an LO drive of +5 dBm across the RF band. A pre-distortion circuit is used to increase the linear input power range of the LO port to above +5 dBm. Discrete amplifiers designed for the IF and RF frequency ports make up the complete upconverter architecture which achieves a conversion gain of 40 dB for an RF output bandwidth of 10 GHz. The upconverter chip set fabricated with InAlAs/InGaAs HBT's demonstrates the widest gain-bandwidth performance of a Gilbert cell based upconverter compared to previous GaAs and InP HBT or Si-bipolar IC's     

Microwave performance of InAlAs/InGaAs/InP MODFET's

Modulation-doped InAlAs/InGaAs/InP structures were grown by molecular beam epitaxy (MBE) and fabricated into FET's with excellent RF gain performance. The intrinsic transconductance was about 400 mS/mm at 300 K. Current gain cutoff frequencies of up to 26.5 GHz were obtained in 1-µm gate devices. Extremely small S12and large S21led to a very largef_{max}of 62 GHz. These results represent the best reported figures for 1-µm devices in this material system and slightly better than those obtained in recently developed pseudomorphic modulation-doped field effect transistors (MODFET's).     

Microwave performance of InGaAs/InAlAs/InP SISFETs

Microwave S-parameter measurements and equivalent-circuit modeling of In_0.53Ga_0.47As/In_0.52Al_0.48 As/InP semiconductor-insulator-semiconductor FETs (SISFETs) of 1.1-μm gate length are discussed. The devices incorporated wide-bandgap buffers, self-aligned contact implants, and refractory air-bridge gates. Their DC I-V characteristics displayed sharp pinchoff, good output conductance of 10-20 mS/ss, and extrinsic transconductance up to 220 ms/mm at room temperature. The maximum unity-current-gain frequency was 27 GHz. Gate resistance was found to be the dominant factor limiting microwave power gain     

GaAs基InAlAs/InGaAsMHEMT直流特性研究

报道了用 MBE技术生长的 Ga As基 In Al As/In Ga As改变结构高电子迁移率晶体管 (MHEMT)的制作过程和器件的直流性能。对于栅长为 0 .8μm的器件 ,最大非本征跨导和饱和电流密度分别为 3 5 0 m S/mm和1 90 m A/mm。源漏击穿电压和栅反向击穿电压分别为 4V和 7.5 V。这些直流特性超过了相同的材料和工艺条件下 Ga As基 PHEMT的水平 ,与 In P基 In Al As/In Ga As HEMT的性能相当     

A p-channel BICFET in the InGaAs/InAlAs material system

The bipolar inversion-channel field-effect transistor (BICFET) relies on a field-effect mechanism to induce and modulate an inversion layer placed at the heterojunction interface. The device was fabricated using molecular beam epitaxy. A current gain of ~15 has been achieved at a current density J of ~8×10³ A/cm² at 300 K. At 77 K, the gain rises to 40 with J=2×10⁴ A/cm². This gain, which follows theoretical predictions, continuously increases with collector current and is limited only by the amount of heat generated in a large-area device. Because of its potential for ballistic transport in the collector, the InGaAs/InAlAs BICFET should be very attractive for high-speed applications     

Optical effect in InAlAs/InGaAs/InP MODFET

Analytical results have been presented for an optically illuminated InAlAs/InGaAs/InP MODFET with an opaque gate. Partial depletion of the active region is considered. The excess carriers due to photo generation are obtained by solving the continuity equation. The energy levels are modified due to the generation of carriers. The surface recombination effect has also been taken into account. The results of I-V characteristics have been compared under dark conditions, since under illumination experimental results are not available. The offset voltage, sheet concentration, I-V, and transconductance have been presented and the effect of illumination discussed     

Striped-channel InAlAs/InGaAs HEMTs with shallow-grating structures

Striped-channel (SC) InAlAs/InGaAs HEMTs have been demonstrated with shallow gratings. The shallow grating structure keeps the gate from touching the channel layer and thus solves the gate leakage problem observed in the deep grating devices on InP substrates. Various channel widths have been realized to study the impact of the channel width on the dc and microwave performance. Due to the enhanced charge control in the SC HEMTs, enhanced transconductance/source-drain current (G_m /I_ds) and transconductance/output conductance (G_m /G_ds) were observed. Compared with conventional HEMTs, the SC HEMTs showed degraded f_T due to additional parasitic capacitances and improved f_max due to better carrier confinement     

InGaAs/InAlAs/InP collector-up microwave heterojunction bipolartransistors

Collector-up InGaAs/InAlAs/InP heterojunction bipolar transistors (HBTs) were successfully fabricated, and their DC and microwave characteristics measured. High collector current density operation (J_c>30 kA/cm²) and high base-emitter junction saturation current density (J₀>10^-7 A/cm²) were achieved. A cutoff frequency of f _t=24 GHz and a maximum frequency of oscillation f _max=20 GHz at a collector current density of J₀ =23 kA/cm² were achieved on a nominal 5-μm×10-μm device