D. A. Humphrey

Ultrahigh Be doping of Ga0.47In0.53As by low‐temperature molecular beam epitaxy

Layers of Ga0.47In0.53As grown on InP by a beam epitaxy method have been doped with Be to p=5×1020 cm−3 by growth at substrate temperatures as low as 365 °C. The maximum doping level is strongly growth temperature dependent. Heterostructure bipolar transistors with base doping p=1×1020 cm−3, current gain β=54, and unity current gain cutoff frequency fT=140 GHz are illustrated.

Near‐ideal lateral scaling in abrupt Al0.48In0.52As/In0.53Ga0.47As heterostructure bipolar transistors prepared by molecular beam epitaxy

We demonstrate near‐ideal lateral scaling in abrupt junction Al0.48In0.52As /In0.53Ga0.47As heterostructure bipolar transistors. Current gain β=162 and 122 has been realized in transistors with emitter stripe width of 50 and 0.6 μm, respectively. The excellent lateral scaling occurs because the 0.5 eV emitter injection energy results in nonequilibrium vertical electron transport in the thin (700 A) InGaAs base.

GaAs/GaInP multiquantum well long‐wavelength infrared detector using bound‐to‐continuum state absorption

We demonstrate an 8 μm superlattice infrared detector which utilizes bound‐to‐continuum state intersubband absorption in lattice‐matched GaAs/Ga0.5In0.5P multiquantum well structures grown by atmospheric pressure metalorganic vapor phase epitaxy. The band offsets of the GaAs/Ga0.5In0.5P heterosystem are obtained by comparing the theoretical absorption spectrum and the measured responsivity spectrum. The values determined for ΔEc and ΔEv are 221 and 262 meV, respectively.

Ka-band monolithic InGaAs/InP HBT VCO's in CPW structure

Two Ka-band monolithic voltage controlled oscillators (VCOs) designed in a coplanar waveguide (CPW) structure are described. Each VCO utilizes an InGaAs/InP heterojunction bipolar transistor (HBT) as the active device and an HBT base-collector junction as the tuning varactor. These two VCOs are biased at a very low voltage of V/sub CE/=1.5 V and the emitter current is less than 10 mA. Under this low dc power dissipation, the VCOs with center frequencies of 26.5 and 33.5 GHz show high dc-to-rf conversion efficiencies over 10% and 5% within the frequency tuning ranges of 1.6 and 1.2 GHz, respectively. The measured phase noise at 1 MHz offset frequency is -110 dBc/Hz. >

Influence of base thickness on collector breakdown in abrupt AlInAs/InGaAs heterostructure bipolar transistors

The avalanche process in the collector of abrupt Al/sub 0.48/In/sub 0.52/As-In/sub 0.53/Ga/sub 0.47/As heterostructure bipolar transistors (HBTs) is reported. It is reported that the collector multiplication constant decreases monotonically with increasing base thickness. When the base thickness is less than the mean-free path for energy relaxation in the base, the avalanche process in the collector is enhanced by high-energy injection from the emitter. On the other hand, no such dependence is observed for long-base transistors with equilibrium base transport. These effects are expected as the emitter injection energy of 0.48 eV is appreciable compared to the impact ionization threshold of 0.83 eV in the InGaAs collector.<<ETX>>

High-frequency submicrometer Al/sub 0.48/In/sub 0.52/As/In/sub 0.53/Ga/sub 0.47/As heterostructure bipolar transistors

The high speed scaling of an Al/sub 0.48/In/sub 0.52/As/In/sub 0.53/Ga/sub 0.47/As submicrometer heterostructure bipolar transistor (HBT) is presented. Transistors with emitter dimensions of 0.5*11 and 3.5*3.5 mu m/sup 2/ exhibit unity current-gain cutoff frequencies of 63 and 70 GHz, respectively. Emitter current density greater than 3.3*10/sup 5/ A/cm/sup 2/ is demonstrated in a submicrometer AlInAs/InGaAs HBT. The analysis shows that the device speed is limited by the parasitic collector charging time.<<ETX>>

Nonequilibrium electron transport in heterostructure bipolar transistors probed by magnetic field

We show that the static current‐voltage characteristics of a heterojunction bipolar transistor are dramatically influenced by application of a magnetic field. Nonequilibrium base transport has a strong influence on collector/emitter breakdown voltage, VCEB. With a magnetic field applied perpendicular to the direction of the injected emitter current VCEB increases from 2.6 V at 0 T to 8 V at 8 T. In the same device with a magnetic field applied parallel to the current flow, the current gain increases by a factor of 2 over the same magnetic field range. Transistors which exploit nonequilibrium base and collector transport have qualitatively different behavior compared to conventional devices which use diffusive and drift‐diffusive transport.

High performance InP/InGaAs heterostructure bipolar transistors grown by metalorganic vapor phase epitaxy

We demonstrate high performance InGaAs/InP heterostructure bipolar transistors grown by metalorganic vapor phase epitaxy. A unity current gain cutoff frequency fT=78 GHz and a maximum oscillation frequency fmax=42 GHz are achieved in transistors with emitter size 2.5×11 μm2. Ring oscillators using nonthreshold logic show a propagation delay of 31 ps.

Carbon doping of Ga0.47In0.53As using carbontetrabromide by metalorganic molecular beam epitaxy for InP‐based heterostructure bipolar transistor devices

Metalorganic molecular beam epitaxy of carbon‐doped heterostructures and InP/Ga0.47In0.53As heterostructure bipolar transistors using carbontetrabromide (CBr4) as the dopant source is reported. Secondary ion mass spectrometry show H incorporation associated with the carbon doping. Hall data for as‐grown and postgrowth annealed samples showed a clear increase in doping only for samples grown at the lowest temperature, 450 °C, and higher doping levels. An increase in the mobility, however, was measured for nearly all samples after annealing, indicating that the neutral C–H complexes most likely contribute to majority carrier scattering. The gain variation for various devices with base thickness, WB, and base doping, p, was found to be nearly proportional to 1/(WB×p)2 consistent with diffusive base transport and Auger dominated recombination in the heavily doped base region. It was also observed that in devices where the C‐doped base was grown at temperatures ≳500 °C, the gain was shifted to much lower value...

Self-aligned thin emitter C-doped base InP/InGaAs/InP DHBT's for high speed digital and microwave IC applications

Summary form only given. We have developed a new self-aligned thin emitter HBT process technology to fabricate high performance InP/InGaAs/InP DHBTs for digital and microwave IC applications. The epistructure which is grown by MOMBE features a C-doped base using a CBr/sub 4/ gas dopant source for stable device operation at high emitter current densities. The process technology uses combined ECR-RIE and wet etching and incorporates self-aligned emitter-base metallizations and spin-on-glass dielectric passivation. The 0.5 /spl mu/m InP collector structure results in much improved common emitter I-V characteristics (compared to InGaAs collectors) with low output conductance and high collector breakdown voltages (8-10 V). The insertion of thin n-doped 30 nm InGaAsP quaternary layers between the InP collector and InGaAs base allows high current density operation (J/sub c/=100 kA/cm/sup 2/) of the DHBT without current blocking. The use of a chirped InP/InGaAs superlattice emitter structure reduces the V/sub be/ of the devices with ideality factors very close to n=1.00. On-wafer s-parameter measurements demonstrated peak values (@J/sub c/=80 kA/cm/sup 2/, V/sub be/=2 V) of f/sub t/=100 GHz and f/sub max/=60 GHz for 2.4/spl times/9.4 /spl mu/m/sup 2/ transistors.