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.     

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.     

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.     

Comparison of the saturated current in normal and inverted modulation-doped In0.53Ga0.47As/InP structures

We measured the saturated current in both normal (doping layer on top) and inverted (doping layer on bottom) structures of modulation-doped In0.53Ga0.47As/InP. In the inverted structure, we find a saturated current consistent with the low-field carrier density and the bulk electron saturated velocity; but for the normal structure the saturated current is significantly lower than expected. Measurements indicate that this low saturation current is due to a loss of carriers at high fields.     

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.     

The electron velocity-field characteristic for n-In0.53Ga0.47As at 300 K

Electron drift velocities in n-type In0.53Ga0.47As have been measured at 300 K using a microwave time-of-flight technique at electric field strengths from about 10 kV/cm to 104 kV/cm. The electron velocity-field characteristic for n-type In0.53Ga0.47As exhibits a larger negative differential mobility and a lower high field velocity than is obtained with GaAs.     

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.     

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.     

An In0.53Ga0.47As/Si3N4n-channel inversion mode MISFET

We describe the operation of an n-channel inversion-mode In0.53Ga0.47As MISFET with a Si3N4insulating layer. This device exhibits a transconductance of 2 mS/mm, which represents an order of magnitude improvement over previously reported In0.53Ga0.47As MISFET results.     

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.     

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.     

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.     

Fabrication and characterization of nonalloyed Cr/Au ohmic contacts to n- and p-type In0.53Ga0.47As

Ion implantation and rapid thermal annealing have been used to selectively produce thin high carrier concentration n- and p-type layers on In0.53Ga0.47As, and nonalloyed ohmic contacts with excellent properties have been achieved by depositing layers of Cr and Au on the implanted regions. The Cr/Au metallization is used to produce ohmic contacts on both p-type and n-type material in the same deposition. A series of electrical test patterns based on the transmission line model and four terminal structure were used to characterize the contact resistance of both alloyed and nonalloyed ohmic contact metallizations on In0.53Ga0.47As. The nonalloyed contacts to n-type material are superior to conventional alloyed contacts made in this study, while the nonalloyed contacts to p-type material are a factor of 5 higher resistance.     

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.     

Low dark-current, high-efficiency planar In0.53Ga0.47As/InP P-I-N photodiodes

We have fabricated high quantum efficiency, high speed, low dark-current In0.53Ga0.47As/InP p-i-n planar photodiodes Which meet the performance requirements of long-wavelength optical communications systems. The diodes employ plasma deposited SiNxas a mask to Zn diffusion. The dark-current density at 10 V is J = 5 × 10^-5A/cm²with a corresponding capacitance of C = 5 × 10^-9F/cm².     

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.     

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.     

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     

An In0.53Ga0.47As p-channel MOSFET with plasma-grown native oxide insulated gate

We describe the operation of an In0.53Ga0.47As p-channel inversion mode MOSFET with plasma grown native oxide insulated gate. This device exhibits a transconductance of 4 mS/mm and an effective channel mobility of more than 50% of the bulk hole mobility. This device is the first demonstration of a native oxide insulated gate MOSFET in the In1-xGaxAsyP1-ymaterial system.     

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.