Po-Hung Lin

Influence of the -doping sheet and setback layer on the performance of an InGaP/GaAs heterojunction bipolar transistor

In this paper, we demonstrate the qualitative influence of a -doping sheet and setback layer on the performance of an InGaP/GaAs heterojunction bipolar transistor (HBT). The results of a theoretical simulation show that the potential spike is reduced by the simultaneous employment of an appropriate setback layer and -doping sheet. Due to the reduction in the potential spike, a high current gain, even at a small collector current regime, and small offset voltage can be attained. Experimentally, an offset voltage as small as 55 mV and current gain of 11 at collector current of A are obtained without a passivation structure.

InGaP/GaAs superlattice-emitter resonant tunneling bipolar transistor (SE-RTBT)

In this letter, a new InGaP/GaAs superlattice-emitter resonant tunneling bipolar transistor (SE-RTBT) is fabricated and demonstrated. A 5-period InGaP/GaAs superlattice is used to serve the RT route and the confinement barrier for minority carriers. Due to the large valence band discontinuity (/spl Delta/E/sub v/) at the InGaP/GaAs heterointerface, a high current gain (/spl beta//sub max//spl sime/220) is obtained. Furthermore, the interesting N-shaped negative-differential-resistance (NDR) phenomena resulting from RT effect are found both in the saturation and forward-active region of current-voltage (I-V) characteristics at room temperature.

Multiple negative-differential-resistance (MNDR) phenomena of a metal-insulator-semiconductor-insulator-metal (MISIM)-like structure with step-compositioned In/sub x/Ga/sub 1-x/As quantum wells

In this paper, a new multiple negative-differential-resistance (MNDR) device based on a metal-insulator-semiconductor-insulator-metal (MISIM)-like structure with step-compositional In/sub x/Ga/sub 1-x/As quantum wells has been fabricated and demonstrated. The interesting MNDR phenomena are found in the current-voltage (I-V) characteristics of this device. At room temperature, the triple switching behaviours and quadruple stable operation states are obtained. In addition, the sixfold switching behaviors and a staircase-shaped I-V characteristic are observed at -105/spl deg/C. A sequential carrier accumulation at InGaAs subwells and the potential lowering process are used to qualitatively explain the interesting MNDR phenomena. From the experimental results, it is shown that the studied device has good potential in multiple-valued logic applications.

On the recombination currents effect of heterostructure-emitter bipolar transistors (HEBTs)

We demonstrate the effect of recombination current on the electrical properties of heterostructure-emitter bipolar transistors (HEBTs). For comparison, an AlGaAs/GaAs and an AlInAs/GaInAs HEBT are fabricated with the layer structure. For the AlGaAs/GaAs HEBT, the hole diffusion length is larger than the emitter thickness, so that most holes can be reflected back at the confinement layer because the hole recombination current is low in the neutral-emitter region. Thus, high emitter injection efficiency and current gain can be achieved simultaneously. On the other hand, for the AlInAs/GaInAs HEBT, the increase of recombination current in the neutral emitter regime and the existence of a potential spike could reduce the emitter injection efficiency at large V/sub BE/ voltage. Hence, the non-1KT component of collector current is enhanced and the transistor characteristics are degraded. However, a lower offset voltage of 40 mV is obtained attributed to the low base surface recombination current for the AlInAs/GaInAs HEBT.

Superlatticed negative differential-resistance heterojunction bipolar transistor

In this article, we report the fabrication of a new superlatticed negative-differential-resistance heterojunction bipolar transistor (SNDR-HBT) based on a lattice-matched Al0.48In0.52As/Ga0.47In0.53As material system. A 20-period AlInAs/GaInAs superlattice is used to serve the resonant tunneling route and the confinement barrier for minority carriers. From experimental results, an extremely low offset voltage of 61 mV and a common-emitter current gain of about 25 has been obtained at room temperature for the non-optimized device, simultaneously. In addition, we also observe the interesting N-shape negative-differential-resistance (NDR) phenomena in both two- and three-terminal operations at 77 K. It is believed that the N-shaped NDR results mainly from resonant tunneling within the 20-period AlInAs/GaInAs superlattice.

AlInAs/InGaAs long-period-superlattice resonant-tunneling transistor (LPSRTT) prepared by MOCVD

We have demonstrated a new GaInAs/AlInAs long-period-superlattice resonant-tunneling transistor (LPSRTT) with 20-period i-AlGaAs/n/sup +/-GaInAs superlattice. The good transistor performances are obtained both 300 K and 77 K. Furthermore, a significant N-shaped NDR phenomenon resulting from resonant tunneling through the superlattice is obtained in the studied LPSRTT device at 77 K.

Modeling and analysis of heterostructure-emitter and heterostructure-base transistors (HEHBTs)

Abstract In this article, we report the DC performances of heterostructure-emitter and heterostructurebase transistors (HEHBTs) by theoretical and experimental analysis. For comparison, the devices with abrupt and graded confinement layer are studied. An analytical model related to the elimination of the potential spike and the recombination components of base current is developed to explain the transistor performances. The experimental current gain of about 280 and 120 are achieved for the devices with abrupt and graded confinement layers, respectively. As a result the excellent confinement effect and negligible neutral recombination in confinement layer for the device with abrupt confinement layer, the current gain is high especially at low emitter-base (E-B) bias regime. Further, the valence band discontinuity (ΔEv) and the emitter injection efficiency are increased attributed to the insertion of InGaAs quantum well (QW) at base region. The offset voltages about of 100 mV are obtained resulted from the elimination of potential spike and low InGaAs surface recombination velocity.

Investigation of a Step-Doped-Channel Negative-Differential-Resistance Transistor

An interesting AlGaAs/InGaAs/GaAs step-doped channel negative-differential-resistance transistor (SDCNDRT) has been fabricated. The SDCNDRT is based on a previously reported step-doped-channel field-effect transistor (SDCFET). The N-shaped negative-differential resistance (NDR) are three-terminal-controlled NDR phenomena. We believe that the NDR phenomena can be attributed to the real space transfer (RST). A maximum drain current and peak-to-valley current ratio (PVCR) of 59 mA and 6.6 are obtained, respectively. The high drain current and PVCR indicate the potential of the SDCFET for practical circuit applications.

Investigation of step-doped channel heterostructure field-effect transistor

Two kinds of heterostructure field-effect transistor (FET) with an InGaAs step-doped-channel (SDC) profile have been fabricated and demonstrated. For the 1/spl times/100 /spl mu/m/sup 2/ gated dimension, the maximum drain saturation currents were 735 and 675 mA/mm, the maximum transconductances 200 and 232 mS/mm, the gate breakdown voltages 15 V and 12 V, and the wide gate voltage swing 3.3 and 2.6 V with transconductance g/sub m/ higher than 150 mS/mm. A simple model is employed to analyze the performance of threshold voltage V/sub T/ and values of -3.7 and -1.8 V are obtained. These good performances show that the SDCFET has a good potential for high-speed, high-power circuit applications.

A new functional AlGaAs/InGaAs/GaAs heterostructure-emitter and heterostructure-base transistor (HEHBT)

A new functional AlGaAs/InGaAs/GaAs heterostructure-emitter and heterostructure-base transistor (HEHBT) with a pseudomorphic base structure is presented. Due to the insertion of an InGaAs quantum well between the emitter-base (E-B) junctions, the valence band discontinuity can be enhanced and a high emitter injection efficiency may be achieved. In addition, an interesting S-shaped multiple negative differential resistance (MNDR) phenomenon is observed under the inverted operation mode. This may be attributed to an avalanche multiplication and sequential two-stage barrier lowering effect resulting from electron accumulation at the AlGaAs/GaAs heterointerface and InGaAs quantum well, respectively.