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.     

Selectively-doped Al0.48In0.52As/Ga0.47In0.53As heterostructure field effect transistor

Selectively-doped depletion-mode FET's which show full pinch-off at 295 K with transconductance in excess of 90 mS/mm and contact resistance less than 0.4 Ω-mm have been fabricated. The device properties reported represent a significant improvement over previously published work on an equivalent structure, because of improvements in growth technique and modifications in the device structure. Analysis of our measurement at room temperature suggests that the two-dimensional electron gas at the hetero-interface is not the dominant contributor to the total device current.     

Depletion mode modulation doped Al0.48In0.52As-Ga0.47In0.53As heterojunction field effect transistors

We report the first demonstration of a depletion mode modulation doped Ga0.47In0.53As field effect transistor. This transistor combines the advantage of modulation doping and the superior material characteristics of Ga0.47In0.53As. DC transconductances of 31 mmho/ mm at 300 K and 69 mmho/mm at 77 K have been measured for a device with 5.2µm gate length and 340 µm gate width. An enhanced drift mobility is responsible for 88 percent of the improvement in the transconductance at 77 K and the remaining 12 percent is attributed to an improved ohmic contact. A high performance modulation doped Ga0.47In0.53As FET is expected to play an important role in very high speed digital and analog applications.     

Electroabsorption Al0.48In0.52As p-i-n avalanche photodiodes grown by molecular beam epitaxy

The operation of the first Al0.48In0.52As p-i-n avalanche photodiode is reported. The i layer has a background doping ≲10¹⁴/ cm³and the diodes have breakdown voltages in excess of -80 V. A strong enhancement of the photoresponse accompanied by avalanche gain at wavelengths near and beyond the band gap is observed, due to the Franz-Keldysh effect. At short wavelengths, an avalanche gain of 50 was measured. A detailed study of different etches to achieve optimum taper of the mesas was also made.     

Ga0.4In0.6As/Al0.55In0.45As pseudomorphic modulation-doped field-effect transistors

High-performance pseudomorphic Ga0.4In0.6As/ Al0.55In0.45As modulation-doped field-effect transistors (MODFET's) grown by MBE on InP have been fabricated and characterized. DC transconductances as high as 271, 227, and 197 mS/mm were obtained at 300K for 1.6-µm and 2.9-µm gate-length enhancement-mode and 2-µm depletion-mode devices, respectively. An average electron velocity as high as 2.36 × 10⁷cm/s has been inferred for the 1.6-µm devices, which is higher than previously reported values for 1-µm gate-length Ga0.47In0.53As/Al0.48In0.52As MODFET's. The higher bandgap Al0.55In0.45As pseudomorphic barrier also offers the advantages of a larger conduction-band discontinuity and a higher Schottky barrier height.     

Inversion-mode insulated gate Ga0.47In0.53As field-effect transistors

It is demonstrated that inversion-mode n-channel insulated gate field-effect transistors can be made of p-type heteroepitaxially-grown Ga0.47In0.53As layers on semi-insulating InP.     

Preparation and properties of molecular beam epitaxy grown (Al0.5Ga0.5)0.48In0.52As

The first reported growth of the quaternary AlGaInAs on an InP substrate by molecular beam epitaxy had an equal aluminum-to-gallium mole fraction ratio, and exhibited a 5 K bandgap energy of 1.237 eV. This is intermediate between the 5 K band gap energy of Ga0.47In0.53As (0.810 eV) and that of Al0.48In0.52As (1.56 eV). A Schottky diode and a MESFET were fabricated on this material.     

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.     

Ga0.72Al0.28As/Ga0.99Be0.01As heterojunction bipolar transistor grown by molecular beam epitaxy

We report the first heterojunction bipolar transistor (HBT) with base doping level as high as 2 × 10²⁰cm^-3. The device is grown by molecular beam epitaxy (MBE) with growth conditions adjusted to keep perfect surface morphology and to avoid dopant diffusion even at ultra-high doping levels. Maximum dc current gain of 10 is observed, for a base thickness of 40 nm. This is a new step in the optimization of HBT's structures for high-speed logic and microwave applications.     

Double heterostructure Ga0.47In0.53As MESFETs by MBE

Ga0.47In0.53As MESFETs have been fabricated on InP substrates. The low barrier height of Ga0.47In0.53As (0.20 eV) which makes simple GaInAs MESFETs at this composition impractical, has been overcome by using thin Al0.48In0.52As layers between gate metal and GaInAs active layers. Al0.48In0.52As has also been exploited in the form of buffer layers. The double heterostructure FET wafers with single crystal Al gate metal were grown by molecular beam epitaxy (MBE). The 2.75 µm gate length MESFETs showed d.c. transconductance gm= 57 mS mm^-1in spite of nonoptimized dimensions.     

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     

Double heterostructure Ga0.47In0.53As MESFETs with submicron gates

MESFETs with GA0.47In0.53As active channel grown by MBE on InP substrates were successfully fabricated. Thin layers of MBE grown Al0.48In0.52As seperated both the single crystal aluminum gate from the active channel and the active channel from the InP substrate so raising the Schottky barrier height of the gate and confining the electrons to the channel. The MESFETs with 0.6µm long gates and gate-to-source separations of 0.8 um exhibited an average gmof 135 mS mm^-1of gate width for Vds= 2V and Vg= 0. This is higher than that reported for GaAs MESFETs with a similar geometry in spite of the intermediate layer between the gate metal and the active layer.     

Ga0.47In0.53As vertical photoconductive detectors with high gain and low bias voltage

We demonstrate for the first time a long-wavelength Ga0.47In0.53As vertical photoconductive detector with very high gain, low noise, low-bias voltages, high sensitivity, and high-coupling efficiency. The detector consists of an n+InP, a Fe-doped Ga0.47In0.53As, and an n+Ga0.47In0.53As layer grown successively on a semi-insulating InP substrate. The highly resistive active layer sandwiched between two n+layers creates a uniform electric field perpendicular to the surface, producing a dc gain of 86 at bias voltages as low as 0.5 V. The noise power at 100 MHz is about 11 dB lower than that of a coplanar interdigitated photoconductive detector prepared with undoped GaInAs grown by vapor-phase epitaxy. Preliminary measurements reveal a receiver sensitivity of -28.2 dBm at a bit-error rate of 10^-9at 420 Mbit/s and a wavelength of 1.55 µm.     

Ion-implanted In0.53Ga0.47As/In0.52Al0.48As lateral PNP transistors

Lateral PNP transistors have been realized for the first time in the (In,Ga)As/(In,Al)As heterostructure material system. Be ion implantation has been used to form the emitter and collector junctions. A current gain of 3.8 is obtained up to 200 µA of collector current for devices with a 1.5 µm electrical base width. A hole diffusion length of 2 µm in the (In,Ga)As is estimated.     

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     

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.     

Integrated double heterostructure Ga0.47In0.53As photoreceiver with automatic gain control

The first operation of an integrated differential notch-type photoconductor and dual gate (DG) double heterostructure (DH) MESFET in Ga0.47In0.53As is reported. The starting material was grown by molecular beam epitaxy on a semi-insulating InP substrate. A 2 mW HeNe laser with a spot diameter Of 0.5 mm could modulate the drain current by 300 µA with the upper gate suitably biased.     

Resistivity increase in MBE Ga0.47In0.53As following ion bombardment

Resistivity increase was compared following various doses of different 100 kV ions implanted into Ga0.47In0.53As. The largest resistivity increase of n-type Ge doped GaInAs resulted from a boron ion implant, and increased to a total of 280 times the original resistivity after heating for 15 minutes at 200°C. Boron ion bombardment can be used to isolate devices in a planar GaInAs integrated circuit process.     

Ga0.47In0.53As: A ternary semiconductor for photodetector applications

Ga0.47In0.53As has been used to make fast (rt < 1 ns), photodiodes with low dark current (i_{D} < 10^{-8}A) and good quantum efficiency (ηQext > 50 percent over the entire1.0-1.7 mum region of the optical spectrum). The physical properties related to the crystal growth and carrier transport are discussed in this paper in terms of both the design and the operating characteristics of detectors fabricated from this ternary alloy. The results of our work show that Ga0.47In0.53As is a material well-suited to several important semiconductor device applications. A comparison to other semiconductor photodiodes shows that Ga0.47In0.53As is one of the most sensitive detectors available in the1.0-1.7 mum wavelength region. One can expect repeater-free transmission in excess of 150 km at 100 Mbits . s^-1using these detectors in a digital optical fiber link at the 1.55 μm low-loss (alpha < 0.3dB . km^-1) low-dispersion transmission window.     

InP/In0.53Ga0.47As heterojunction phototransistors grown by chemical beam epitaxy

We describe InP/In0.53Ga0.47As heterojunction phototransistors (HPT's) grown by chemical beam epitaxy (CBE). These devices exhibit high gain ( > 150) at signal levels as low as - 50 dBm. Compared to earlier devices of this type, the gain is relatively independent of the optical signal level. This is due primarily to the improved quality of the emitter-base heterojunction interface which, for these HPT's, is characterized by an ideality factor of 1.14. At an incident power level of -21 dBm the bandwidth is 14 MHz and the gain-bandwidth product is 4.8 GHz.