In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As abrupt double-heterojunction bipolar transistors

In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As n-p-n abrupt double-heterojunction bipolar transistors grown by molecular beam epitaxy (MBE) have been realized for the first time. DC current gains in excess of 300 have been measured on devices operated in the emitter-up configuration. DC current gains around 50 are obtained on device structures with Be+ implanted extrinsic base regions operated in the emitter-down configuration. The carrier injection and collection behavior of the abrupt InGaAs/InAlAs heterojunctions is discussed.     

Studies on an In0.53Ga0.47As/In0.52Al0.48As single-quantum-well quasi-MISFET

We describe here the properties of a novel InGaAs/ InAlAs quasi-MISFET in which an inverted modulation-doped single quantum well forms the channel and an undoped semi-insulating InAlAs constitutes the gate barrier. The entire structure is grown lattice-matched to InP continuously by molecular-beam epitaxy in a single step. Rapid thermal annealing of implanted semiconductors and ohmic contacts have been investigated and have been used successfully in the fabrication of the MISFET's. Improved performance is obtained with the incorporation of Ti in the source-drain metallization, with which contact resistances as low as 0.1 ω . mm are measured. Charge-control modeling of the proposed device predicts the carrier concentration in the channel region fairly well at room temperature. A quantum mechanical modeling of the device in the effective mass approximation also has been done. The thickness of the InAlAs doping layer is found to be an important parameter that controls the device turn-on characteristics. The velocity-field characteristics of the two-dimensional channel electrons were measured by pulse current-voltage and pulsed Hall techniques. The maximum velocities measured at 300 and 77 K are 1.5 × 10⁷and 1.7 × 10⁷cm/s, respectively. Fairly high electron mobilities are measured in single-quantum-well MISFET structures even with well thicknesses as small as 100 Å. The InAlAs gate barrier is effective in reducing the gate leakage current. Gate leakage currents are reduced further with a composite dielectric consisting of oxidized Al and InAlAs. An extrinsic transconductance of 310 mS/mm is measured in a 1.0-µm gate device at 300 K. A value of fT= 32 GHz, measured in a 1.0-µm device, is the best obtained so far with this material system. It is expected that submicrometer gate lengths will lead to even better performance.     

Anomalous effects of lamp annealing in modulation-doped In0.53Ga0.47As/In0.52Al0.48As and Si-implanted In0.53Ga0.47As

The effects of pulsed halogen-lamp annealing on modulation-doped In0.53Ga0.47As/In0.52Al0.48As heterostructures and Si-implanted In0.53Ga0.47As have been studied to determine the suitabiiity of this process in the fabrication of high-performance field-effect transistors. Implantation and annealing of these materials are necessary for contact and self-aligned gate formation. Mobilities as high as 7400 cm²/ V . s are measured at 300 K in undoped molecular-beam epitaxy In-GaAs implanted with 8 × 10¹²cm^{-2 29}Si⁺and lamp annealed at 700°C for 5 s. Anomalous overactivations (up to 120 percent) are observed in these layers When silox encapsulation is used during annealing, but the effect is absent for GaAs proximity capping. Sharp decreases in sheet-electron concentration and mobility occur in the normal modulation-doped structures for annealing temperatures > 750°C, while this trend is much smaller in the inverted structures. Arsenic loss from the In-AlAs doping layer is attributed as the main mechanism for this behavior, which makes the inverted structure more suitable for device processing. Depth profiling in the modulation-doped structures indicates that there may be serious pinchoff problems in these devices when annealed at higher temperatures due to outdiffusion of impurities from the InP substrate. Values of interdiffusion coefficients at the InGaAs/ InAIAs heterointerfaces, being reported for the first time, are almost three orders higher than those measured in the GaAs/AIAs systems.     

A In0.53Ga0.47As-In0.52Al0.48As single quantum well field-effect transistor

This letter reports the materials characteristics and device performance of a In0.53Ga0.47As-In0.52Al0.48As single quantum well (SQW) field-effect transistor grown by molecular beam epitaxy on     

Design and performance of very high-speed In0.53Ga0.47As/In0.52Al0.48As p-i-n photodiodes grown by molecular beam epitaxy

High-speed In0.53Ga0.47As/In0.52Al0.48As photodiodes have been grown by molecular beam epitaxy (MBE) on semi-insulating InP substrates and fabricated. The measured impulse response characteristics are very close to the analytically calculated ones. The temporal response to pulsed optical excitation is characterized by a rise time of 21 ps and a width (FWHM) of 27 ps. The 25 × 20-µm²diodes have a junction capacitance <0.1 pF, a dark current ∼1 nA, and a peak responsivity of 0.35 A/W. These characteristics are comparable or better than most epitaxial InGaAs photodiodes reported to date and make the devices suitable for a host of high-speed applications and monolithic integration.     

Low-resistance ohmic contacts to AlGaAs/GaAs and In0.52Al0.48As/In0.53Ga0.47As modulation-doped structures obtained by halogen lamp annealing

The successful application of short-term halogen lamp annealing to form ohmic contacts to AlGaAs/GaAs and In0.52Al0.48As/ In0.53Ga0.47As modulation-doped structures is demonstrated. Use of Ti in the electron-beam evaporated metallization scheme and a two-step annealing cycle give contacts with reproducibly good electrical and morphological characteristics. Minimum values of specific contact resistancerho_{c} = 4.0 times 10^{-7}and6.0 times 10^{-7}Ω.cm²for AlGaAs/GaAs and In0.52Al0.48As/In0.53Ga0.47As, respectively, are measured. Corresponding values of the transfer resistance Rcare 0.12 ± 0.02 and 0.18 ± 0.05 Ω.mm. These values are the lowest achieved with lamp annealing and are comparable to the best obtained with transient furnace annealing.     

Interface roughness scattering in normal and inverted In0.53Ga0.47As—In0.52Al0.48As modulation-doped heterostructures

A new model for interface roughness scattering in modulation-doped (MD) heterostructures, based on the physical structure of a molecular beam epitaxy- (MBE) grown heterointerface, is formulated. The parameters describing interface roughness have been derived from growth studies and analysis of photoluminescence linewidths of quantum wells. The model has been applied to analyze low-temperature electron mobilities in normal and inverted In0.53Ga0.47As-In0.52Al0.48As MD heterostructures. It is found that the mobility in the normal heterostructure is limited by alloy scattering, whereas both alloy and interface roughness scattering play equally dominant roles in the inverted structure.     

An In0.52Al0.48As/n+-In0.53Ga0.47As MISFET with a heavily doped channel

An In0.52Al0.48As/n⁺-In0.53Ga0.47As MIS-type field-effect transistor (FET) with a channel doped at a 7 × 10¹⁷cm^-3level has been fabricated on an InP substrate. A device with a 2-µm channel length has yielded a maximum transconductance of 152 mS/mm,f_{T} = 12.4GHz, andf_{max} = 50GHz. At 10 GHz, the maximum available gain is 17.4 dB. The performance of this device shows that heavily doped channel FET's are very promising for high-frequency operation.     

An In0.53Ga0.47As junction field-effect transistor

Preliminary results are reported for the operation of a junction field-effect transistor fabricated from In0.53Ga0.47As grown lattice-matched to an InP:Fe substrate.     

A proposal for a high-speed In0.52Al0.48As/In0.53Ga0.47As MODFET with an (InAs)m(GaAs)msuperlattice channel

In this letter we examine theoretically the potential of an In0.52Al0.48As/In0.53Ga0.47As modulation-doped field-effect transistor in which the usual InGaAs channel is replaced by an (InAs)m(GaAs)msuperlattice with m ≲ 4, extending over 100 ∼ 200 Å from the InAlAs interface. For small m the superlattice bandstructure is essentially the same as that of the alloy and the effects of the very small lattice mismatch are negligible. More importantly, the electrons in the active channel are not expected to suffer any alloy scattering since the channel now has perfect long-range order with no random potential fluctuations. We show that this MODFET has extremely high mobility and its low-temperature mobility can be an order of magnitude higher than that of the conventional InAlAs/InGaAs MODFET. Comparison is also made with the AlGaAs/GaAs MODFET and results indicate that the proposed structure has superior potential performance.     

In0.53Ga0.47As submicrometer FET's Grown by MBE

We describe the fabrication process for InGaAs submicrometer gate JFET's, using Be ion implantation and wet chemical etching. A gate length as small as 0.5 µm can be formed by this technique. Such FET's made on MBE-grown material bad a dc trans-conductance as high as 85 mS/mm and showed a high power-handling capability.     

In0.53Ga0.47As FET's with insulator-assisted Schottky gates

Schottky-gate FET's have been fabricated on n-type In0.53Ga0.47As using a thin interfacial silicon nitride layer between the metal and the epitaxial layer to reduce the gate leakage current. In0.53Ga0.47As was grown by molecular beam epitaxy on semi-insulating InP substrates and silicon nitride was grown by plasma-enhanced chemical vapor deposition. Devices with 1.2µm gate length and net donor doping in the mid 10¹⁶cm^-3range show dc transconductance of up to 130mS/mm. Both depletion and enhancement mode operation were observed. The effective saturation velocity of electrons in the channel is deduced to be 2.0 ± 0.5 × 10⁷cm/sec, a value 60 to 70% higher than that in GaAs MESFET's. The insulator-assisted gate technology has many advantages in fabrication flexibility and control compared with other approaches to realizing high-speed microwave and logic in FET's in In0.53Ga0.47As.     

Planar type vapor-phase epitaxial In0.53Ga0.47As photodiode

A punch-through type planar photodiode with low dark current and high speed response was fabricated from low carrier density In0.53Ga0.47As grown by vapor-phase epitaxy. Dark current density was 3.1 × 10^-5A/cm²at 10 V bias. Rise time and full width at half maximum were 82 and 126 psec, respectively, at a bias above 4 V.     

Performance of In0.53Ga0.47As/InP avalanche photodiodes

We calculate operating characteristics of high-sensitivity high-speed In0.53Ga0.47As/InP avalanche photodiodes (APD's). We find that significant photocurrent gain is obtained for a total fixed-charge density ofsigma_{tot} > 3 times 10^{12}cm^-2in the depleted InP and0.53Ga0.47As regions. To obtain high quantum efficiency and low tunneling currents, the fixed-charge density in the InP must be in the range2 times 10^{12}cm^-2leq sigma_{B} leq 3 times 10^{12}cm^-2. We calculate the breakdown voltages for APD's with uniformly doped layers and find that practical detectors with avalanche breakdowns as low as 15 V can be realized. High quantum efficiency and fast response are obtained by compositional grading of the In0.53Ga0.47As heterointerface over a distance ofL gsim 380Å, depending on the doping and amount of the In0.53Ga0.47As layer swept out at breakdown. Finally, a comparison of calculations with experimental results is presented.     

Junction field-effect transistors using In0.53Ga0.47As material grown by molecular beam epitaxy

In this article we discusss the fabrication of junction field-effect transistors (JFETs) using In0.53Ga0.47As grown p-n junction material prepared by molecular beam epitaxy (MBE). For an n-channel doping of 2 × 10¹⁶cm^-3and a gate length of 2.0µm, these devices are shown to have a transconductance of 50 mS/mm with a corresponding internal transconductance of 67 mS/mm.     

A long-wavelength, annular In0.53Ga0.47As p-i-n photodetector

We describe a novel, annular In0.53Ga0.47As p-in photodiode sensitive to λ = 1.7 µm for use as a fiber tap or front-face laser monitor. The diode has a 150 µm diameter, straight-walled hole through the diode cross-section formed by photochemical etching. The hole is concentric with the 430 µm diameter mesa. A dark current of I = 90 nA at 5 V and a breakdown voltage of 33 V indicate that the hole formation process does not result in significant degradation of the device operating characteristics. Measurements of photoresponse as a function of position across the diode surface give further evidence that the hole does not effect overall device performance.     

Self-aligned In0.53Ga0.47As/semi-insulating/n+InP junction field-effect transistors

Depletion-mode junction field-effect transistors (JFET's) with InGaAs p-n junctions grown on compensated Fe:InP or highly resistive In0.52Al0.48As isolation layers grown on n⁺-InP substrates have been fabricated using a combination of molecular-beam epitaxy and metalorganic chemical vapor deposition growth techniques. Using a self-aligned gate technology with a 1-µm gate length, devices with high transconductance (80 mS/mm), low leakage current (<100 nA), and a gate-to-source capacitance of 0.4 pF have been fabricated. This is apparently the first report where InP-based alloy FET's have been fabricated on an isolated n⁺-substrate. This structure has application to monolithically integrated photoreceivers.     

Investigation of In0.53Ga0.47As for high-frequency microwave power FET's

Submicrometer In0.53Ga0.47As junction field-effect transistors (JFET's) were fabricated using a chemical etching technique. In spite of the well-known low bulk breakdown fields of InGaAs, the source-drain breakdown voltages of the FET's were close to 20 V under pinchoff conditions, indicating a potentially high power-handling capability. At 11 GHz, a 250-µm-wide FET showed a linear gain of 5.2 dB and 17.2-dB . m (53 mW) output power at 1-dB compression point, with a power-added efficiency of 14 percent. Problems of an unexpectedly low electron mobility in the channel, annealing of implanted Be, and oscillations in the drain current-voltage characteristic are discussed.     

Low-noise In0.53Ga0.47As:Fe photoconductive detectors for optical communication

Photoconductive detectors were fabricated on In0.53- Ga0.47As/InP made high-resistive by doping with elemental Fe. A mobility of ∼ 6000 cm²/V . s and a net electron concentration of (2-5) × 10¹²cm^-3were measured in layers on which the devices were fabricated. Photoconductive gains of 5-10 were measured with CW and pulsed excitation. The calculation response time to 300-ps pulsed excitation is ∼ 100 ps and can be improved with reduced channel spacings. Typical dark currents in the devices are of the order of 50 µ A at room temperature. The noise power into a 50-Ω load measured at 82°C is -108.9 dBm. This is the lowest value measured in photoconductive detectors made with III-V In0.53Ga0.47As.     

Short channel Ga0.47In0.53As/Al0.48In0.52As selectively doped field effect transistors

We report a selectively doped Ga0.47In0.53As/Al0.48In0.52As field effect transistor with a 1.2 µm gate length and present a model of two-region operation to analyze its I-V characteristics. This depletion mode transistor shows complete pinch-off and saturation characteristics with a low frequency transconductance of 70 mmho/ mm at 300 K and 125 mmho/mm at 77 K. The theoretical model, which includes the background carriers in the undoped Ga0.47In0.52As layer, agrees with the experimental results.