K. Ikossi-Anastasiou

Low-temperature characterization of high-current-gain graded-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 AA, 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.<<ETX>>

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/sup 4/ A/cm/sup 2/, and a p-n-p AlGaAs/GaAs HBT with a superlattice GaAsSb emitter ohmic contact which has a specific contact resistivity of 5+or-1*10/sup -7/ Omega -cm/sup 2/ across the sample, are examined. >

Gain enhancement in InAlAs/InGaAs heterojunction bipolar transistors using an emitter ledge

Improved gain was observed at low currents when a thin emitter ledge was incorporated into npn In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistors. A 40‐nm‐thick n‐In0.52Al0.48As emitter ledge resulted in over four times higher gain at low biases due to reduced surface recombination.

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

Abstract 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.

Interface states in regrown GaAs p‐n junctions by selective molecular beam epitaxy

We report the first evaluation of interface states present in GaAs p‐n junctions regrown on a SiO2 masked substrate by selective molecular beam epitaxy. A constant‐capacitance deep‐level transient spectroscopy (CC‐DLTS) method is extended to the regrown p‐n junction case, and a technique to distinguish the DLTS signal emerging from bulk and interface states is employed. The extracted interface state density is in good agreement with predictions based on the unified disorder‐induced gap state model.

A high-gain (Ga,Al)As/GaAs heterostructure bipolar transistor with an 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-10/sup 3/ A cm/sup -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.<<ETX>>

Exploratory antimony containing heterojunction bipolar transistors

The advantages of using Sb containing III-V compounds in bipolar type devices are discussed with recent experimental results of two different applications of GaAsSb in Heterojunction Bipolar Transistors (HBTs). The performance of a prototype AlGaAs/GaAsSb/GaAs double HBT (DHBT) that exhibits a current gain of five and a maximum collector current density of 5 X 104 A/cm2 and a pnp AlGaAs/GaAs HBT with a superlattice GaAsSb emitter ohmic contact, with specific contact resistivity of 5 +/- 1 X 10-7 (Omega) -cm2 across the sample, are examined.

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

AlGaAs/GaAs Narrow Base Heterojunction Bipolar Transistors (NBHBTs) with 50 angstroms thick bases exhibit maximum small signal common emitter current gains hfe 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 is saturates around 200 K, suggesting a tunnelling limited current transport mechanism.