An n-channel BICFET in the InGaAs/InAlGaAs/InAlAs material system

An n-channel BICFET in the InGaAs/InAlGaAs/InAlAs material system with a current gain in a large-area device of greater than 900 is discussed. The device structure utilizes a self-aligned refractory emitter contact and high-temperature processing and still obtains an ideality factor of 1.2 for the source input diode     

Demonstration of a p-channel GaAs/AlGaAs BICFET

The p-channel bipolar inversion-channel field-effect transistor (BICFET) is a bipolar transistor which utilizes an inversion layer induced by planar doping using molecular beam epitaxy. A current gain of ~8 is obtained at a current density of ~8×10³ A/cm². The results agree well with previous theoretical predictions of current gain, output conductance, and collector offset voltage. There is no base transit time in the BICFET and thus the speed of the device will be determined by transit-time-limited transport in the collector     

Demonstration of a p-channel BICFET in the GexSi1-x/Si system

Operational bipolar inversion-channel field-effect transistors (BICFETs) based on the Ge_xSi_1-x/Si system are discussed. The 300 K current gain of β=365 at a current density of J_c=2.5×10⁴ A/cm² is the highest value reported for any BICFET to date. The use of a double-heterojunction inversion channel eliminates the collector offset voltage. The present devices are limited by the channel resistance, so that performance improvements are expected for laterally-scaled-down devices     

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     

An n-channel BICFET in the GaAs/AlGaAs material system

An n-channel BICFET (bipolar inversion channel FET) and an HFET (heterojunction FET) have been fabricated for the first time by MBE (molecular-beam epitaxy) growth with the charge sheet located on the wide-bandgap side of the heterointerface. This implementation is most desirable because of the potential for low resistance, high gain, and a temperature-stable structure. The HFET associated with the BICFET has a positive threshold, indicating that no channel exists in the equilibrium state     

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.     

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     

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     

InP/InAlAs/InGaAs quantum wires

Single InGaAs quantum wires and stacked InGaAs quantum wires with InAIAs barriers have been fabricated on V-grooved InP substrates by low pressure metal-organic chemical vapour deposition (MOCVD). We have found growth conditions where the InAIAs barrier exhibits a resharpening effect, similar to that of AlGaAs utilized for growth on GaAs substrates. The existence of structural and electronic quantum wires in the bottom of the grooves is proven.     

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     

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     

Electron mobility and drift velocity in selectively doped InAlAs/InGaAs/InAlAs heterostructures

An increase in the electron mobility and drift velocity in high electric fields in quantum wells of selectively doped InAlAs/InGaAs/InAsAs heterostructures is obtained experimentally via controlling the composition of semiconductors forming the interface. The electron mobility at the interface in the In_0.8Ga_0.2As/In_0.7Al_0.3As metamorphic structure with a high molar fraction of In (0.7–0.8) is as high as 12.3 × 10³ cm² V⁻¹ s⁻¹ at room temperature. An increase in the electron mobility by a factor of 1.1–1.4 is attained upon the introduction of thin (1–3 nm) InAs layers into a quantum well of selectively doped In_0.53Ga_0.47As/In_0.52Al_0.48As heterostructures. A maximal drift velocity attains 2.5 × 10⁷ cm/s in electric fields of 2–5 kV/cm. The threshold field F _th for the intervalley Γ-L electron transfer (the Gunn effect) in the InGaAs quantum well is higher than in the bulk material by a factor of 2.5–3. The effect of two- to threefold decrease in the threshold field F _th in the InGaAs quantum well is established upon increasing the molar fraction of In in the InAlAs barrier, as well as upon the introduction of thin InAs inserts into the InGaAs quantum well.     

High-field transport in InGaAs/InAlAs modulation-doped heterostructures

The velocity-field and mobility-field characteristics of normal and inverted InGaAs/InAlAs modulation-doped heterostructures grown by molecular-beam epitaxy have been measured at 300 and 77 K. Veloczities of 3.0 × 10⁷and 1.7 × 10⁷cm/s have been measured in the normal and inverted structures, respectively, at 77 K. Current instabilities are observed at the corresponding field values. Hall mobilities decrease With field beyond 500 V/cm, principally due to phonon scattering. The mobilities in normal and inverted heterostructures attain Similar values at fields higher than 1 kV/cm, irrespective of the low-field values.     

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-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     

Processing techniques for InGaAs/InAlAs/InGaAs spin field effect transistors

Wet etch processing techniques for InGaAs/InAl/As/InGaAs transistors are used to fabricate an N-channel HEMT (High Electron Mobility Transistor) with Fe contacts. These processing techniques can easily be extended for dilute magnetic semiconductor regrowth and for testing of various spin injection geometries.     

A physical model for the kink effect in InAlAs/InGaAs HEMTs

We present a new model for the the kink effect in InAlAs/InGaAs HEMTs. The model suggests that the kink is due to a threshold voltage shift which arises from a hole pile-up in the extrinsic source and an ensuing charging of the surface and/or the buffer-substrate interface. The model captures many of the observed behaviors of the kink, including the kink's dependence on bias, time, temperature, illumination, and device structure. Using the model, we have developed a simple equivalent circuit, which reproduced well the kink's dc characteristics, its time evolution in the nanosecond range, and its dependence on illumination     

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     

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     

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