S.C. Feng

High-performance InGaP/In x Ga/sub 1-x/As HEMT with an inverted delta-doped V-shaped channel structure

This letter reports a new and high-performance InGaP/In/sub x/Ga/sub 1-x/As high electron mobility transistor (HEMT) with an inverted delta-doped V-shaped channel. Due to the presence of V-shaped inverted delta-doped InGaP/In/sub x/Ga/sub 1-x/As structure, good carrier confinement and a flat and wide transconductance operation regime are expected. Experimentally, the fabricated device (1/spl times/100 /spl mu/m/sup 2/) shows a high gate-to-drain breakdown voltage of 30 V and a high output drain saturation current density of 826 mA/mm at V/sub GS/=2.5 V. The high transconductance expands over a very broad operation range with the maximum value of 201 mS/mm at 300 K. Meanwhile, the studied device exhibits a good microwave frequency linearity.

On the multiple negative-differential-resistance (MNDR) InGaP-GaAs resonant tunneling bipolar transistors

Two InGaP/GaAs resonant tunneling bipolar transistors (RTBTs) with different superlattice (SL) structures in the emitters are fabricated and studied. The uniform and modulated widths of barriers are respectively utilized in the specific SL structures. Based on the calculations, the ground state and first excited state minibands are estimated from the transmission probability. The electron transport of RT through SL structures is significantly determined by the electric field behaviors across the barriers. Experimentally, the excellent transistor characteristics including the small saturation voltage, small offset voltage and high breakdown voltages are obtained due to the insertion of /spl delta/-doping sheet at the base-collector (B-C) heterointerface. Furthermore, at higher current regimes, the double- and quaternary-negative difference resistance (NDR) phenomena are observed in agreement with the theoretical prediction at 300 K.

Applications of an In0.53Ga0.25Al0.22As/InP continuous-conduction-band structure for ultralow current operation transistors

Based on the compositional dependence on the conduction band discontinuity, a significant heterojunction bipolar transistor (HBT) with a continuous conduction band heterointerface between the InP emitter and the In0.53Ga0.25Al0.22As base is fabricated. Experimentally, due to the elimination of the potential spike, a very low offset voltage of 50 mV is observed. Also, the studied device exhibits better breakdown characteristics and lower output conductance as compared with other InP/InGaAs or AlInAs/InGaAs HBTs. Furthermore, attributed to the enhancement of the hole confinement by an inserted δ-doped sheet at the emitter–base interface, a dramatic current gain about 4 is found even under an ultralow current operation regime (IC⩽5 nA).

Observation of the impulse-like negative-differential resistance of superlatticed resonant-tunneling transistor

An AlInAs/GaInAs superlatticed resonant-tunneling transistor (SRTT) is fabricated and demonstrated. A five-period AlInAs/GaInAs superlattice is used to provide resonant tunneling (RT) and confinement of minority carriers. Experimentally, an interesting impulse-like multiple negative-differential-resistance (MNDR) phenomenon and transistor action are obtained for the studied SRTT device at room temperature. It is believed that the N-shaped MNDR results mainly from RT within the five-period AlInAs/GaInAs superlattice.

Investigation of an InGaP/GaAs resonant-tunneling heterojunction bipolar transistor

Abstract An interesting InGaP/GaAs resonant-tunneling heterojunction bipolar transistor incorporating a superlattice (SL) structure in the emitter has been fabricated and studied. With the n-type doped well, the strongly coupling effect dominating the biased SL behaves like a double barrier operation. On the basis of the transfer matrix method, the transport mechanism of sequential miniband conduction can be developed by the theoretical calculation associated with the RT in the studied SL structure. Experimentally, the double negative differential resistance phenomena are presented both in the two-and three-terminal current–voltage characteristics at 300 K. In addition, excellent transistor behaviors including the high dc current gain as high as 70, low saturation voltage smaller than 1.2 V, low offset voltage of 110 mV and high breakdown voltage larger than 20 V are obtained.

Characteristics of InGaP/GaAs delta-doped heterojunction bipolar transistor

An InGaP/GaAs heterojunction bipolar transistor with a δ-doped sheet structure has been fabricated successfully. High current gain, especially in the very low collector current regime, low collector-emitter offset voltage (ΔVCE) characteristics are obtained. There is an extremely small offset voltage of about 55 meV due to the elimination of the potential spike at the emitter-base heterojunction by a δ-doped sheet and a 50 A very thin setback layer. On the other hand, the high current gain of 280 also reveals that the degradation of current gain due to the potential spike can be avoided. In addition, the influence of the δ-doped sheet and the undoped setback on device properties is studied.

Design consideration of emitter-base junction structure for InGaP/GaAs heterojunction bipolar transistor

An InGaP/GaAs heterojunction bipolar transistor (HBT) with an 50 /spl Aring/ undoped spacer and /spl delta/-doping sheet at base-emitter heterointerface is fabricated and studied. A common-emitter current gain of 280 and an offset voltage as small as 55 mV are obtained, respectively. This results show that high current gain and low offset voltage can be attained simultaneously without the passivation of emitter-base junction. From the experimental results, it shows that the potential spike is indeed reduced by the employment of an /spl delta/-doped layer and spacer simultaneously. On the other hand, theoretical consideration also shows that the potential spike is removed by inserting a /spl delta/-doping sheet between the emitter-base heterointerface.

On the AlInAs/GaInAs superlatticed negative-differential-resistance transistor (SNDRT)

A new AlInAs/GaInAs superlattice negative-differential-resistance switch (SNDRT) is fabricated successfully and demonstrated. A 5-period AlInAs/GaInAs superlattice is used to serve the resonant tunneling route and the confinement barrier for minority carriers. Experimentally, an interesting three-terminal-controlled N-shaped multiple negative-differential-resistance (MNDR) phenomenon and transistor action are obtained for the studied SNDRT device in the saturation and forward active mode at room temperature, respectively. It is believed that the N-shaped MNDR results mainly from resonant tunneling within the 5-period AlInAs/GaInAs superlattice.

Temperature-Dependent Character istics of a Novel InP/InGaAlAs Heterojunction Bipolar Transistor

In this work, we report the temperature-dependent characteristics of a new InP/InGaAlAs heterojunction bipolar transistor (HBT). In order to improve the DC performance of conventional InGaAsbased single HBT’s, the quaternary In0.53Ga0.34Al0.13As with a wider band gap is employed as the material for both the base and collector layers. Experimentally, the studied device exhibits a relatively high common-emitter breakdown voltage and a low output conductance even at high temperature operations. Furthermore, the temperature dependence of current gain and breakdown voltage is studied and demonstrated.

A Novel Functional Negative-Differential-Resistance Heterojunction Bipolar Transistor (NDR-HBT)

A novel functional negative-differentialresistance heterojunction bipolar transistor (NDR-HBT) has been successfully fabricated and demonstrated. The studied device acts as a conventional HBT for the applied higher base current of IB=100μA/step. However, the NDR phenomenon with interesting topee-shaped current-voltage characteristics was observed under the applied base current of IB=2μA/step. These are attributed to the use of narrow base width and δ-doped sheet in the studied device. Besides, the N-shaped NDR phenomena are obviously observed under the applied tungsten light source. The peak-to-valley current ratio (PVCR) up to 1.5 is obtained for the base current IB=60μA. The photocurrent is about 1.01mA and keeps constantly under the applied higher base current.