Growth of Ga0.47In0.53As on InP by low-pressure m.o. c.v.d.

The first heteroepitaxy is reported of Ga0.47In0.53As on InP by low-pressure metalorganic chemical vapour deposition (m.o. c.v.d.). Triethylindium (t.e.i.) and triethylgallium (t.e.g) were used as group III sources, and arsine as the group V source. These Ga0.47In0.53As epilayers exhibit high electron mobility (7.74 cm2 V?1 s?1 for a total impurity concentration of 2.5 × 1016 cm?3 at 300 K) and a photoluminescence efficiency comparable to l.p.e. layers. The lattice mismatch is only ?a0/a0 ? 4 × 10?4. Our mobility measurements indicate that m.o. c.v.d. Ga0.47In0.53As is a promising material for microwave device applications.     

Substrate dependence of InP m.e.s.f.e.t. performance

There is evidence to suggest that Fe outdiffuses, during the growth, into the epitaxial films prepared by vapour-phase epitaxy at 650°C. Field-effect transistors on Fe-doped material show substantial looping that was absent on Cr-doped material and exhibit about 2 dB worse noise figure at about 7 GHz. Experiments with low 1015 S-doped InP grown on Sn-, Cr- and Fe-doped substates indicate that such outdiffusion is typically about 5 ?m. Saturation velocity levels in the m.e.s.f.e.t. channel are about 1.7 × 107 cm/s and 1.3 × 107 cm/s, associated with Cr and Fe doped substrates, respectively.     

Microwave power amplification with InP f.e.t.s

InP f.e.t.s were fabricated from v.p.e. layers, with an Al gate of 1.5 ?m × 308 ?m. The power output at 9 GHz, with 4 dB gain, was 1.15 W/mm gate width. This result is believed to be higher than the best published results obtained with equivalent GaAs f.e.t. structures.     

Microwave InxGa1?xAsyP1?y/InP f.e.t

Microwave performance of InxGa1?xAsyP1?y quaternary alloy metal-semiconductor field effect transistors (m.e.s.f.e.t.s) is reported. Liquid-phase epitaxy (l.p.e.) using a step cooling technique has been employed to grow submicrometre quaternary layers having room-temperature bandgaps of 0.9, 1.0, 1.05, 1.15 and 1.2eV. F.E.T.s having gate dimensions of 1×200 ?m and a channel length of 5 ?m have been fabricated using 1.15 and 1.2 eV quaternary alloys. A maximum d.c. transconductance of about 10 mS and a maximum available gain of about 7 dB at 10 GHz have been obtained.     

Effects of growth temperature and [PH3]/[In(C2H5)3] on purity of epitaxial InP grown by metalorganic chemical vapour deposition

High-purity undoped InP epitaxial layers (ND ? NA = 5 × 1014 cm?3, ?77?105 cm2/Vs) are grown by low-pressure metalorganic chemical vapour deposition. The carrier concentrations decrease and the electron mobilities increase as the growth temperature decreases from 700°C to 575°C and the mole fraction ratios ([PH3]/[In(C2H5)3]) increase from 29 to 290.     

Dual wavelength surface emitting InGaAsP l.e.d.s

Surface emitting l.e.d.s capable of simultaneous emission near 1.14 ?m and 1.3 ?m wavelengths, from an area 75 ?m × 75 ?m. have been fabricated and tested. Outputs of 0.5 mW and 0.8 mW, respectively, were obtained at the two wavelengths in initial devices driven at 50 mA d c. The measured crosstalk was ?23.9 dB (electrical).     

Low-noise microwave f.e.t.s fabricated by molecular-beam epitaxy

The growth of m.b.e. GaAs suitable for f.e.t. fabrication is reported. The m.b.e. structure consists of an n+ = 2.5×1018 cm?3 contact layer on top of an n+ = 3.5×1017 cm?3 active layer. Using this material, f.e.t.s. have been fabricated that have a minimum noise figure of 1.5 dB with an associated gain of 15 dB at 8 GHz. These are the best results yet reported for low-noise m.b.e. GaAs f.e.t.s.     

GaAs m.e.s.f.e.t. linear power-amplifier stage giving 1 W

A balanced GaAs m.e.s.f.e.t. power stage has been developed for the 7?8 GHz satellite communication frequency band. At 7.5 GHz, the output power at 1 dB comparession 1 W with a power added efficiency of 37%. The small-signal gain was 6.65 ± 0.45 dB across the frequency band. The small-signal gain, phase, group delay and input and output v.s.w.r. as function of frequency are described. Large-signal gain saturation and 3rd-order intermodulation distrotion measurements are also presented.     

Dual-gate m.e.s.f.e.t. self-oscillating X-band mixers

GaAs dual-gate m.e.s.f.e.t.s have been successfully used as self-oscillating down-convertors in X-band. A single device replaces the preamplifier, mixer and local oscillator. The best conversion gain achieved by mixing from 10 GHz down to 1 GHz was 12 dB. The input (gate 1) to output (drain) port isolation amounted to 16 dB. Slug-tuner and `disc?-resonator circuits were tested and showed comparable gain and noise performance. Best d.s.b. noise figures of 5.5 dB could be realised at an i.f. of 1 GHz with an associated conversion gain of 4 dB.     

1.55 /spl mu/m bottom-emitting InAlGaAs VCSELs with Al/sub 2/O/sub 3//a-Si thin-film pairs as top mirror

A a 1.55 /spl mu/m InAlGaAs/InP vertical-cavity surface-emitting laser grown by metal-organic chemical vapour deposition is presented. Al/sub 2/O/sub 3//a-Si thin-film pairs and InAlGaAs/InAlAs epitaxial layers are used as a top mirror and a bottom-side output coupler, respectively. Direct modulation characteristics through singlemode fibre are reported at a speed of 2.5 Gbit/s.     

GaAs power m.e.s.f.e.t.s. with a graded recess structure

A new recess structure device was developed to improve the field distrubution and therfore the performance of GaAs power m.e.s.f.e.t.s. The linear gain and the output power were improved by 1?2 dB for this structure. The highest output powers obtained are 15 W with 4 dB associated gain at 6 GHz, and 4.3 W with 3 dB associated gain at 11 GHz.     

GaAs heterojunction f.e.t. with epitaxial Ge gate

A Ge heterojunction-gate GaAs f.e.t. has been developed using p-type epitaxial Ge gates deposited by vacuum evaporation on heated n-type GaAs substrates. Boron-ion implantation of the gate and an aluminium overlay was used to lower the gate resistance. A typical 8 ?m gate-length device exhibited a noise figure of 5.2 dB with 4.5 dB associated gain at 1.8 GHz.     

7.9?8.4 GHz GaAs m.e.s.f.e.t. amplifier

A 4-stage balanced GaAs m.e.s.f.e.t. amplifier has been developed for the 7.9?8.4 GHz satellite-communication frequency band. Linear gain of 26±0.5dB and 150 mW power at 1 dB compression were obtained across the design band. The small-signal gain, phase linearity, group delay and noise figure are described as a function of frequency. Large-signal gain saturation, 3rd-order intermodulation distortion, gain and phase against temperature and a.m.-to-p.m. conversion data are also presented.     

First successful fabrication of high-performance all-refractory-metal (Ta-Au) GaAs FET using very highly doped N+-layers and nonalloyed ohmic contacts

An all-refractory-metal GaAs MESFET (ARFET) making use of a Ta Schottky barrier with a thick gold overlayer for the source, gate and drain, and very highly doped N+-layers (2x1019 cm-3) to achieve low-resistivity nonalloyed ohmic contacts, has been successfully fabricated. These have a 400 ?m gate periphery and 0.6 ?m gate length and measured an associated gain of 10.22 dB and a noise figure of 2.14 dB at 8 GHz. The ARFETs were fabricated on epitaxial layers grown by MBE. Only one mask was used to simultaneously define source, gate and drain regions via a plasma dry-etch technique.     

Two-dimensional electron gas at interface of a selectively doped InGaP/GaAs heterostructure

We report the first observation of a two-dimensional electron gas at the interface of an InGaP/GaAs heterojunction. The closely lattice-matched (?a/a?5×10?4) epitaxial layers of InGaP were grown by vapour levitation epitaxy using a chloride transport technique with a resulting interface sheet carrier concentration of 7×1011 cm?2.     

Operation of 6 GHz f.e.t. amplifier at reduced ambient temperature

An m.i.c. f.e.t. amplifier was tested at ambient temperatures varying, from 20 to ?85°C. A gain increase of 3 dB and noise figure decrease of 1.9 dB were measured over that temperature range.     

GaAs f.e.t.s with silicon-implanted channels

Field-effect transistors with channel doping profiles fabricated by the implantation of silicon ions into high-resistivity vapour phase epitaxial GaAs have given noise figures of 2.9 dB with an associated gain of approximately 5 dB at 10 GHz. Similar measurements on F.E.T.S fabricated in an identical manner, except for the channel fabrication, where silicon ions were implanted directly into a Cr-doped semi-insulating GaAs substrate, have resulted in nose figures typically 1 dB higher.     

Dual gate GaAs m.e.s.f.e.t. phase shifter with gain at 12 GHz

A dual gate m.e.s.f.e.t. phase shifter is described with 4 dB insertion gain at 12 GHz and more than 100° linear continuous phase shift as a function of the d.c. voltage applied to the controlling gate electrode.     

Low-loss fibre prepared under high deposition rate by modified c.v.d. technique

Graded-index fibres with a GeO2-P2O5-SiO2 core have been prepared by a modified c.v.d. and drawing process. The deposition rate of the core glass was 0.17 cm3/min (0.37 g/min), and the fibres have an attenuation of 2.6 dB/km at 0.83 ?m and a 6 dB bandwidth of 816 MHz km.     

GaAs/GaAlAs asymmetric Mach-Zehnder demultiplexer with reduced polarization dependence

A two-channel GaAs/AlGaAs asymmetric Mach-Zehnder wavelength demultiplexer with reduced polarization dependence was demonstrated. The device was fabricated on a single heterostructure comprising a 1.45- mu m-thick layer of GaAs on a 6.0- mu m-thick Ga/sub 0.85/Al/sub 0.15/As buffer layer. The epitaxial layers were grown by MOCVD (metalorganic chemical vapor deposition) on an n/sup +/ GaAs substrate. The single-mode rib waveguides, 3 mu m wide and 0.29 mu m high, were fabricated using standard photolithographic techniques followed by chemical etch and removal of the resist mask. Extinction ratios of 24.1 dB for transverse electric (TE) and 22.5 dB for transverse magnetic (TM) polarized light were measured on a device with an anti-reflection coating on its input and output facets. The active length of the device is approximately 6.5 mm and total loss of 1.1 dB was obtained in a 16-mm-long chip.<>