A high-gain (Ga,Al)As/GaAs heterostructure bipolar transistor withan equilibrium-depleted spike-doped base

The fabrication is reported of a high-gain (Ga,Al)As/GaAs heterostructure bipolar transistor (HBT) with a p-spike-doped base that is depleted at equilibrium. The device structure, based on that proposed for a bipolar inversion-channel field-effect transistor (BICFET), was grown by molecular-beam epitaxy (MBE). Fabricated transistors, containing an AlAs/n-GaAs superlattice emitter layer, exhibited DC current gains of up to 500. Maximum current gains of tested devices occurred at collector current densities in the mid-10³ A cm ^-2 range. It is postulated that the induced base in these transistors is formed predominantly by the forward-bias action on the base-emitter junction     

InAlAs/InGaAs heterojunction bipolar transistors with AlAs etch-stop layer

A seven monolayer AlAs layer was used as an etch stop at the emitter-base heterojunction of an Npn In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As HBT. The etch-stop HBTs displayed higher DC gain and similar microwave performance when compared to devices without the AlAs layer.<>     

Double heterojunction bipolar transistor in Al/sub x/Ga/sub 1-x/As/GaAs/sub 1-y/Sb/sub y/ system

Double heterojunction bipolar transistors based on the Al/sub x/Ga/sub 1-x/As/GaAs/sub 1-y/Sb/sub y/ system are examined. The base layer consists of narrow band gap GaAs/sub 1-y/Sb/sub y/ and the emitter and collector consist of wider band gap Al/sub x/Ga/sub 1-x/As. Preliminary experimental results show that AlGaAs/GaAsSb/GaAs DHBTs exhibit a current gain of five and a maximum collector current density of 5*10/sup 4/ A/cm/sup 2/.<>     

GaAsSb for heterojunction bipolar transistors

The advantages of using GaAsSb in heterojunction bipolar transistors (HBT) are discussed with emphasis on two recent experimental results in the AlGaAs/GaAsSb material system. The performances of a prototype n-p-n AlGaAs/GaAsSb/GaAs double HBT (DHBT) that exhibits stable current gain with maximum collector current density of 5×10 ⁴ A/cm², and a p-n-p AlGaAs/GaAs HBT with a superlattice GaAsSb emitter ohmic contact which has a specific contact resistivity of 5±1×10^-7 Ω-cm² across the sample, are examined     

Low-temperature characterization of high-current-gaingraded-emitter AlGaAs/GaAs narrow-base heterojunction bipolar transistor

Narrow-based heterojunction bipolar transistors (NBHBTs) in the AlGaAs/GaAs material system, with a nominal base thickness of 50 Å, exhibit maximum small-signal common-emitter current gains of 1400 at 300 K and 3000 at 80 K. The performance of the device is attributed to the superlattice graded-emitter contact and a novel planar base access fabrication process. Low-temperature measurements indicate that the maximum current gain increases exponentially with decreasing temperature until it saturates around 200 K, suggesting a tunneling-limited current transport mechanism     

Early voltage in heterojunction bipolar transistors: Quantum tunneling and base recombination effects

An extension of the thermionic emission expression for Early voltage V_A for heterojunction bipolar transistors including quantum mechanical tunneling and base recombination effects is provided. The theoretical model is based on a single flux treatment of the carrier transport invoking the concise notation of scattering matrices. V_A is numerically evaluated under the WKB quantum mechanical approximation for triangular and parabolic barriers. The temperature dependence of the Early voltage is simulated numerically and compared to earlier theoretical V_A predictions and actual experimental results of V_A in heterojunction bipolar transistors.