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In this paper, a simple and nondestructive method of modeling 40-nm interconnects is proposed. Traditional methods based on charge-based capacitance measurement model the interconnects by fitting the capacitance or resistance curves, first by assuming one constant process parameter, such as metal thickness, and then by extracting the metal width, metal spacing, and interlevel dielectric (ILD) thickness from certain test patterns that may therefore result in model inaccuracy while the transmission and scanning electron microscopy methods are both destructive and time consuming. The proposed new methodology directly extracts the metal width based on the metal resistance test structures, and then the metal thickness, metal spacing, and ILD thickness without any presumption. It is also nondestructive and fast, with a model accuracy higher than 95%. Furthermore, with the ensured accuracy of layout parameter extraction, the necessity of an accurate interconnect model in the 40 nm technology and beyond is emphasized.

The interesting hydrogen sensing characteristics of two transistors with an Al 0.24 Ga 0.76 As (device A) and In 0.49 Ga 0.51 P (device B) Schottky layer are demonstrated and studied. Experimentally, device A shows a lower hydrogen detection limit of 4.3 ppm H 2 /air, a higher current variation of 7.79 mA and a shorter adsorption time of 10.95 s in a 9970 ppm H 2 /air at room temperature. On the other hand, device B exhibits more stable hydrogen-sensing characteristics at high temperatures. Even at a low concentration of 14 ppm H 2 /air the hydrogen sensing properties of device B can be obtained as the temperature increases from 30 to 160 °C. Because the Al 0.24 Ga 0.76 As and In 0.49 Ga 0.51 P materials are lattice-matched to the GaAs substrate, the studied devices can be integrated as sensor arrays to obtain superior hydrogen sensing characteristics including higher sensing signals, lower detection limit, shorter response time, and widespread detection and temperature regimes.

An interesting hydrogen sensor based on an Al/sub 0.24/Ga/sub 0.76/As Schottky barrier high-electron mobility transistor with a catalytic Pd metal/oxide/semiconductor is fabricated and demonstrated. In comparison with traditional Schottky diodes or capacitance-voltage type hydrogen sensors, the studied device exhibits larger current variation, lower hydrogen detection limit, and shorter transient hydrogen response time. Besides, good hydrogen-sensing properties, such as significant drain current change, threshold voltage shift, and transconductance change of transistor behaviors, are obtained. Therefore, the studied device provides the promise for high-performance solid-state hydrogen sensors, optoelectronic integrated circuits, and microelectromechanical system applications.

An interesting hydrogen sensor based on a high electron mobility transistor (HEMT) device with a Pd–oxide–In0.49Ga0.51P gate structure is fabricated and demonstrated. The hydrogen sensing characteristics including hydrogen detection sensitivity and transient responses of the studied device under different hydrogen concentrations and temperature are measured and studied. The hydrogen detection sensitivity is related to a change in the contact potential at the Pd/insulator interface. The kinetic and thermodynamic properties of hydrogen adsorption are also studied. Experimentally, good hydrogen detection sensitivities, large magnitude of current variations (3.96 mA in 9970 ppm H2/air gas at room temperature) and shorter absorption response time (22 s in 9970 ppm H2/air gas at room temperature) are obtained for a 1.4 μm × 100 μm gate dimension device. Therefore, the studied device provides a promise for high-performance solid-state hydrogen sensor, integrated circuit (IC) and micro electro-mechanical system (MEMS) applications.

An interesting hydrogen sensor based on a Pt–oxide–Al0.3Ga0.7As MOS structure is fabricated and studied. The transient response and hydrogen detection sensitivity of the studied device under different hydrogen concentrations, temperature and applied voltages are measured. In addition, the kinetic and thermodynamic properties of hydrogen adsorption are studied and discussed. Experimentally, the studied device shows significant advantages of extremely low hydrogen concentration (15 ppm H2/air) detection capability, high hydrogen detection sensitivity (20 in 9090 ppm H2/air gas), short response time, wide temperature operating regime and good hydrogen detection ability under bi-directional applied bias. Based on these good properties, therefore, the studied device provides a promise for high-performance solid-state hydrogen sensor applications.

Pd/InGaP hydrogen sensors based on the metal-oxide-semiconductor (MOS) and metal-semiconductor Schottky diodes have been fabricated and systematically studied. The effects of hydrogen adsorption on device performances such as the current-voltage characteristics, barrier height variation, hydrogen coverage, and heat of adsorption are investigated. The studied devices exhibit very wide hydrogen concentration detection regimes and remarkable hydrogen-sensing properties. Particularly, an extremely low hydrogen concentration of 15 ppm H/sub 2//air at room temperature can be detected. In addition, under the presence of oxide layers in the studied MOS device structure, the enhancements of barrier height and high-temperature operating capability are observed. The initial heat of adsorption for Pd/oxide and Pd/semiconductor interface are calculated as 355 and 65.9 meV/atom, respectively. Furthermore, the considerably short response times are found in studied devices.

The hydrogen response characteristics and sensing properties or catalytic Pd/Al/sub 0.3/Ga/sub 0.7/As metal-oxide-semiconductor (MOS) and metal-semiconductor (MS) Schottky diodes are systematically studied. The effects of hydrogen adsorption on device performances such as the current-voltage characteristics, sensitivity, barrier height variation, heat of adsorption, and transient response are investigated. The studied devices can be operated under very wide hydrogen concentration regimes with remarkable hydrogen-sensing properties. Particularly, at an extremely low hydrogen concentration of 15 ppm H/sub 2//air, both steady-state and transient responses at room temperature can be detected. In addition, under the presence of oxide layer in the studied MOS device, a larger change of barrier height and higher hydrogen response are observed. In addition, according to the van't Hoff equation, the initial values of heat adsorption for Pd/semiconductor and Pd/oxide interface are calculated as 7.29 and 49.6 KJ/mole, respectively.

A new Pt/oxide/InGaP metal-oxide semiconductor (MOS) Schottky diode has been fabricated and studied. Upon exposure to hydrogen, the steady-state and transient responses under different hydrogen concentrations and temperatures are measured. Due to the inherent property of InGaP material, e.g. the wide energy gap, a wide hydrogen-sensing range as large as 300 K (from room temperature to 600 K) is obtained. Even at room temperature, a very high sensitivity over 500% for 9090 ppm hydrogen in air is acquired. Furthermore, the measured absorption response time is less than 1 s at the applied voltage of 0.7 V and 9090 ppm hydrogen concentration atmosphere condition. Simultaneously, based on the analysis of the variation of barrier height and hydrogen coverage, the characteristics of the studied Pt/oxide/InGaP MOS Schottky diode is in good agreement with the Lundstrom isotherm.

The dc performances of a novel InP-InGaAs tunneling emitter bipolar transistor (TEBT) are studied and demonstrated. The studied device can be operated under an extremely wide collector current regime larger than 11 decades in magnitude (10/sup -12/ to 10/sup -1/ A). A current gain of 3 is obtained even operated at an ultralow collector current of 3.9/spl times/10/sup -12/ A (1.56 /spl times/10/sup -7/ A/cm/sup 2/). The common-emitter and common-base breakdown voltages of the studied device are higher than 2 and 5 V, respectively. Furthermore, a very low collector-emitter offset voltage of 40 mV is found. The temperature-dependent dc characteristics of the TEBT are measured and studied. Consequentially, based on experimental results, the studied device provides the promise for low-power electronics applications.

A new InGaP-InGaAs-GaAs double channel pseudomorphic high-electron mobility transistor (DC-PHEMT) has been fabricated successfully. The detailed temperature-dependent performance is investigated. The key features of the studied device are the use of an InGaAs DC structure, triple /spl delta/-doped carrier supplier layers and good Schottky behavior of the InGaP "insulator". For a 1-/spl mu/m gate length device, the turn-on voltage of 1.46 (1.16) V, gate leakage current of 60 [600] /spl mu/A/mm at V/sub GD/ = 15 V, maximum extrinsic transconductance of 162 [145] mS/mm with 310 [260] mA/mm broad operation regime (> 0.9g/sub m,max/), output conductance of 0.41 (0.43) mS/mm, and voltage gain of 390 [335] are obtained at T = 300 [480] K, respectively. In addition, good microwave performance with a flat and wide operation regime is obtained.

The temperature-dependent characteristics of an n+-InGaAs/n-GaAs composite doped channel (CDC) heterostructure field-effect transistor (HFET) have been studied. Due to the reduction of leakage current and good carrier confinement in the n+-InGaAs/n-GaAs CDC structure, the degradation of device performances with increasing the temperature is insignificant. Experimentally, for a 1 x 100 μm2 device, the gate-drain breakdown voltage of 24.5 (22.0) V, turn-on voltage of 2.05 (1.70) V, off-state drain-source breakdown voltage of 24.4 (18.7) V, transconductance of 161 (138) mS/mm, output conductance of 0.60 (0.60) mS/mm, and voltage gain of 268 (230) are obtained at 300 (450) K, respectively. The shift of Vth from 300 to 450 K is only 13 mV. In addition, the studied device also shows good microwave performances with flat and wide operation regime.

A novel and high-performance Pd/oxide/GaAs hydrogen sensor based on a metal-insulator-semiconductor field-effect transistor (MISFET) is fabricated and studied. In the presence of the interfacial oxide, high sensitivity and significant increase in output drain current are observed. In the presence of hydrogen, a 2×200 µm2 gate dimension device shows good dc characteristics including high turn-on voltage, an obvious variation of drain current and a short response time. In addition, under the applied voltage of -4 V and 537 ppm hydrogen in air, a very high sensitivity of 9473 is obtained. This performance shows that the device studied has a good potential for high-speed and high-sensitivity hydrogen sensor and MISFET integrated circuit applications.

In this work, the off-state breakdown characteristics of two different types InGaP-based high-barrier gate heterostructure field-effect transistors are studied and demonstrated. These devices have different high-barrier gate structures, e.g. the i-InGaP layer for device A and n + - GaAs/p + -InGaP/n-GaAs camel-like structure for device B. The wide-gap InGaP layer is used to improve the breakdown characteristics. Experimentally, the studied devices show high off-state breakdown characteristics even at high temperature operation regime. This indicates that the studied devices are suitable for high-power and high-temperature applications. In addition, the off-state breakdown mechanisms are different for device A and B. For device A, off-state breakdown characteristics is only gate dominated at the temperature regime from 30 to 180 ∘ C. For device B, off-state breakdown characteristics are gate and channel dominated at 30 ∘ C and only gate dominated within 150 to 210 ∘ C.

The InGaP/InGaAs single and double delta-doped pseudomorphic high electron mobility transistor (δ-PHEMT) grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD) have been fabricated and investigated. Based on the employment of the wide-gap InGaP Schottky layer and delta-doped carrier supplier, the high breakdown voltages together with good device characteristics are obtained simultaneously. Furthermore, the newly designed V-shaped InGaAs channel can enhance the carrier confinement effect and increase the product of carrier concentration and mobility. Experimentally, for 1×100 μm 2 devices, the gate-to-drain breakdown voltages larger than 40 (30) V, the transconductances of 90 (201) mS/mm, and the maximum current densities of 646 (846) mA/mm are achieved for the studied single and double δ-PHEMT, respectively. Meanwhile, the measured f T and f max are 12 (16) GHz and 28.4 (34) GHz, respectively.

A new S-shaped switch based on the InP/InGaAlAs material system has been successfully fabricated and demonstrated. Due to the avalanche multiplication and potential redistribution process, the interesting multiple-negative-differential-resistance (MNDR) is found under the inverted operation mode at room temperature. The three-terminal NDR characteristics are investigated under the applied base current I B . Moreover, the anomalous multiple-route and multiple-step current-voltage (I-V) characteristics at 77K are also observed. The switching behaviors demonstrate that the proposed structure is a good candidate for multiple-valued logic applications.

A new heterostructure field-effect transistor (HFET) with GaAs/InGaP camel-like gate and GaAs/InGaAs channel structure has been fabricated by MOCVD. The studied device exhibits a large barrier height, high breakdown voltage, and low leakage current even at high temperature environments. Experimentally, for a 1×100 μ m 2 device, the gate-drain breakdown voltage and gate leakage current are 52 (31.5) V, and 37 μ A/mm (3.5 mA/mm) at the gate-drain voltage of 40 V, respectively, at the temperature of 300 (480) K. The high drain-source operation voltage over 20 V with low leakage current is also obtained. These good performances provide the promise for high-breakdown and high-temperature operations.

A newly designed inverted delta-doped V-shaped GaInP/In/sub x/Ga/sub 1-x/As/GaAs pseudomorphic high electron mobility transistor (PHEMT) has been successfully fabricated and studied. For a 1/spl times/100 /spl mu/m/sup 2/ device, a high gate-to-drain breakdown voltage over 30 V at 300 K is found. In addition, a maximum transconductance of 201 mS/mm with a broad operation regime for 3 V of gate bias (565 mA/mm of drain current density), a very high output drain saturation current density of 826 mA/mm, and a high DC gain ratio of 575 are obtained. Furthermore, good temperature-dependent performances at the operating temperature ranging from 300 to 450 K are found. The unity current gain cutoff frequency f/sub T/ and maximum oscillation frequency f/sub max/ up to 16 and 34 GHz are obtained, respectively. Meanwhile, the studied device shows the significantly wide and flat gate bias operation regime (3 V) for microwave performances.

A novel photonic-sensitive InAlGaAs/InP negative-differential-resistance heterojunction bipolar transistor (NDR-HBT) is fabricated and demonstrated. Due to the appropriately designed narrow base width and the employment of a δ -doped sheet at the emitter–base (E–B ) heterojunction, the base resistance effect results in the significant NDR phenomenon. In addition, the experimental results show that the device studied is very sensitive to the applied light source. The N-shaped NDR phenomena are clearly observed under illumination. This phenomenon is attributed to the base resistance and barrier lowering effect resulting from holes induced by the applied light source.

A novel narrow-base heterojunction bipolar transistor and a multiple-state switching device based on the InP/InGaAlAs material system have been fabricated and demonstrated. Common-emitter current gains up to 28 and 25 are obtained. Due to the use of an InGaAlAs narrow base, interesting topee-shaped current-voltage characteristics presented in the transistor active regime and negative-differential-resistance (NDR) loci are observed under the applied base current of IB = 2 µA/step. In addition, multiple-route and multiple-state S-shaped NDR characteristics are observed at 77 K due to the insertion of the InGaAs quantum well in the base-collector junction. The topee-shaped NDR phenomena are attributed to the modulation of the potential spike at the base-emitter heterojunction. However, the switching behaviours are due to the avalanche multiplication, confinement effect and two-stage barrier lowering effect.

Temperature-dependent dc performances of lattice-matched InP/InGaAlAs heterojunction bipolar transistors (HBTs) using the InGaAlAs quaternary alloy as the base and collector layers are studied and reported. When compared with conventional InP/InGaAs HBTs, the device studied exhibits a higher common-emitter breakdown voltage and a lower output conductance even at high temperature. The variations of offset voltage and ideality factor at different temperatures have been analysed. In addition, with decreasing temperature from 25 °C toward -196 °C, an irregular temperature behaviour of current gain is observed. At high current levels, the temperature-dependent current gain is mainly determined by the reduced reverse hole injection current. As the current level is lowered, the dominance of reverse hole injection current is correspondingly replaced by the recombination current.

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 InGaAs-based single HBTs, the quaternary In/sub 0.53/Ga/sub 0.34/Al/sub 0.13/As with a wider bandgap 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 low output conductance even at high temperature. Based on the breakdown mechanism of avalanche multiplication, the negative temperature dependence of breakdown voltage is attributed to the positive temperature-dependent impact ionization coefficient. Furthermore, the temperature dependence of current gain is investigated and reported. It is believed that the suppression of hole injection current with decreasing temperature is responsible for the opposite variation of current gains at high current levels.

A novel multiple-state switching device based on an InP/AlInGaAs heterojunction bipolar transistor (HBT) structure has been successfully fabricated and demonstrated. The common-emitter current gain up to 25 is obtained under the forward operation mode. However, the anomalous multiple-negative-differential-resistance (MNDR) phenomena controlled either by electrical or optical input signals are observed under the inverted operation mode. The studied device exhibits a single-route S-shaped NDR behavior in the dark and a distinct significant S-shaped MNDR phenomena by introducing an incident light source at room temperature. Moreover, the anomalous multiple-route and multiple-step current-voltage (I-V) characteristics are also observed at 77 K. The switching behaviors are attributed to the avalanche multiplication, barrier lowering effect and potential redistribution process. Experimental results show that the studied device provides a good potentiality for multiple-valued logic and optoelectronic switching system applications.

Novel double delta-doped sheet (D3 S) Ga0.51 In0.49 P/In0.15 Ga0.85 As/Ga0.51 In0.49 P pseudomorphic high-electron-mobility transistors (PHEMTs) have been fabricated successfully and studied. A wide-gap Ga0.51 In0.49 P Schottky layer and a D3 S structure are used to improve device performance. Furthermore, an airbridge-gate structure is employed to achieve good dc and RF performances. For a 1 µm gate length device, a high gate-to-drain breakdown voltage over 35 V, an available output current density up to 615 mA mm-1 , a maximum transconductance of 110 mS mm-1 and a high dc gain ratio of 487 are obtained. On the other hand, the maximum values of unity current gain cut-off frequency fT and maximum oscillation frequency fmax are 19.5 and 40.5 GHz, respectively. The output power of 15.6 dB m (363 mW mm-1 ), power gain of 5.6 dB, power added efficiency (PAE) of 37% and drain efficiency (DE) of 51% are obtained at an input power of 10 dB m and the measured frequency of 2.4 GHz.

8/spl times/4 cm/sup 2/ single-sided p/sup +/-i (or v)-n/sup +/ silicon microstrip sensors with coupling capacitors and polysilicon bias resistors were fabricated with the planar technology, and various techniques used to reduce the leakage currents of sensors and their results are presented. Different gettering processes have been employed to remove the impurities and defects from the sensor active regions, and the Electronic Research and Service Organization (ERSOs) Charge-Coupled Device (CCD) gettering technique, combined with backside polysilicon and oxide-nitride-oxide (ONO) deposition process, was found to be the most effective and suitable one. From the measurement results of the special p/sup +/-i (or v)-n/sup +/ junction test structures, it was found that the sensor leakage current mainly came from the side-wall leakage of its p/sup +/-strip. A modified LOCal Oxidation of Silicon (LOGOS) isolation process has been used to reduce this side-wall leakage. Also, the Sirtl-etch analysis of the sensor revealed that the side-wall leakage current has been caused by residual boron-implantation defects after annealing. These defects would concentrate along the edge of p/sup +/-strip and be enhanced to cause dislocations by the film-edge-induced stress effect. Several annealing techniques have also been studied to remove the boron-implantation damages. The fabricated prototype sensors have been tested in a beam at the CERN Super Proton Synchrotron area. The test results showed that the sensor concept under study is feasible.

In this paper, we will demonstrate two new InGaAs-GaAs pseudomorphic heterostructure transistors prepared by MOVPE technology, i.e. InGaAs-GaAs graded-concentration doping-channel MIS-like field effect transistors (FET) and heterostructure-emitter and heterostructure-base (InGaAs-GaAs) transistors (HEHBT). For the doping-channel MIS-like FET, the graded In 0.15 Ga 0.85 As doping-channel structure is employed as the active channel. For a 0.8 × 100 μ m 2 gate device, a breakdown voltage of 15 V, a maximum transconductance of 200 mS/mm, and a maximum drain saturation current of 735 mA/mm are obtained. For the HEHBT, the confinement effect for holes is enhanced owing to the presence of GaAs/InGaAs/GaAs quantum wells. Thus, the emitter injection efficiency is increased and a high current gain can be obtained. Also, due to the lower surface recombination velocity of InGaAs base layers, the potential spike of the emitter-base (E-B) junction can be reduced significantly. This can provide a lower collector-emitter offset voltage. For an emitter area of 4.9 × 10 −5 cm 2 , the common emitter current gain of 120 and the collector-emitter offset voltage of 100 mV are obtained.

A n+-GaAs/p+-In0.49Ga0.51P/n-GaAs camel-like gate structure has been applied to fabricate high-performance transistors. The studied heterostructure field-effect transistor exhibits a large barrier height, high breakdown voltage, low leakage current, and good temperature-dependent characteristics. Experimentally, for a 1×100 μm2 device, the gate-drain breakdown voltage and gate leakage current are 52 (31.5) V, and 37 μ A/mm (3.5 mA/mm) at the gate-drain voltage of 40 V, respectively, at the temperature of 300 (480) K. In addition, the high drain-source operation voltage over 20 V with low leakage current is obtained.

The characteristics of polysilicon resistors in sub-0.25 /spl mu/m CMOS ULSI applications have been studied. Based on the presented sub-0.25 /spl mu/m CMOS borderless contact, both n/sup +/ and p/sup +/ polysilicon resistors with Ti- and Co-salicide self-aligned process are used at the ends of each resistor. A simple and useful model is proposed to analyze and calculate the essential parameters of polysilicon resistors including electrical delta W(/spl Delta/W), interface resistance R/sub interface/, and pure sheet resistance R/sub pure/. This approach can substantially help engineers in designing and fabricating the precise polysilicon resistors in sub-0.25 /spl mu/m CMOS technology.

A novel double ion-implant Ti-salicide technology combining As pre-amorphization implant plus Si ion-mixing implant without the additional lithography process has been developed successfully and reported. Based on this technology, the good performances of uniform Ti-silicide formation, low and narrow distribution of sheet resistances both on n/sup +//p/sup +/ poly-gate and source/drain diffusion layers, and lower leakage currents in the n/sup +//p-well and p/sup +//n-well junctions are obtained simultaneously. In addition, excellent behavior of a 0.24-/spl mu/m NMOSFET and PMOSFET fabricated by this technology are also achieved.

A GaAs‐InGaP switch has been fabricated and demonstrated. In this device, double i‐InGaP layers are employed to provide the potential barriers for carrier tunneling and hole confinement. As sufficient external voltage is applied to this device, a double S‐shaped negative‐differential‐ resistance (NDR) characteristics is obtained resulting from the sequential avalanche multiplications in the high electric field regions. However, because of the poor confinement effect to holes, only a single S‐shaped NDR phenomenon is observed at higher temperature. With device parameters appropriately adjusted, this device may show prominent potential for multiple‐valued logic applications.

An interesting InGaP/InGaAs quantum-well delta-doped-channel field-effect transistor is fabricated and demonstrated. Due to the employed InGaAs dual quantum-well delta-doped-channel structure and Schottky behaviors of InGaP "insulator," good DC properties including higher turn-on voltage, lower leakage current, better linearity, and good RF performances are obtained. In addition, the experimental results are fitted well with theoretical simulation data based on a two-dimensional simulator. Moreover, the studied device exhibits relatively negligible temperature-dependent characteristics over wide operating temperature region (300

In Chinese, zero anaphors occur frequently. This talk discusses several issues in identification of zero anaphors. Syntactic tagging of words in a running text for detection of anaphora requires specification of argument structure for verbal elements. Verbs requiring a subject or an object can be used to locate the position of zero anaphors. Typical argument structures for verbs, however, often do not take into account the expansion of the structure in discourse such as placing the instrument in object position. Once the place of a zero anaphor is located, the discourse processor will attempt to recover the entity. There may be more than one entity in the previous context that can fit in the argument structure of the verb. It has been discussed in the literature that the recovery of zero anaphors requires extra-linguistic knowledge. However, I will discuss two recovery principles that utilize linguistic information as given in the text. The opening statement of a topic continuity normally provides the element for ellipsis in the statements that follow. So the first principle is to return to the opening statement for recovery. Perceptive verbs, on the other hand, often trigger the search of anaphors in the most recent element. This recency principle can be broken by certain adverbial expressions that mark the turn of the event. These principles apply within a topic continuity. The size of a topic continuity is empirically determined to be about 50 words with some variation.

For enhancing hydrogen detecting ability. a high-performance hydrogen sensor based on a high electron mobility transistor structure by utilising a Pd/oxide/Al 0.24 Ga 0.76 As MOS structure is fabricated and investigated. At different temperatures, hydrogen-sensing characteristics of the studied device under steady- and transition-state with different concentration hydrogen gases are measured. Even at an extremely low hydrogen concentration of 4.3 ppm H 2 /air, the current modulation can be found significantly. Furthermore, in comparison with other FET-type hydrogen sensors, under 9970 ppm H 2 /air, the studied device exhibits a much shorter response time of 10.95 s.

The dc performances of an interesting InP/InGaAs tunneling-emitter bipolar transistor (TEBT) with double heterostructures are studied and demonstrated. The studied device has a higher breakdown voltage than conventional InP single heterojunction bipolar transistors between the collector and base. The base–collector junction breakdown voltage VBR up to 15.6 V is obtained. Both of the common-emitter and common-base breakdown voltages of the studied device are higher than 10 V. Furthermore, low variations of dc current gains are found as the temperature is increased from 25 to 175 °C. The elimination of knee-shaped characteristics and near unity ideality factors of collector and base currents (ηC and ηB) are obtained due to the use of a δ-doping sheet and spacer layer. In addition, the studied TEBT device has a stable dc current gain distributed regime as the temperature is increased from 25 to 175 °C.

A highly hydrogen-sensitive Pd/InP metal-oxide-semiconductor (MOS) Schottky diode hydrogen sensor is presented. The role of donor level in the interfacial oxide layer replacing the amphoteric native defects leads to enhanced barrier height and high sensitivity. According to reaction kinetics studies, the maximum change in barrier height achieves 0.31 eV. Short response and recovery times in the transient characteristics demonstrate the high hydrogen adsorption and desorption rates at high temperatures.

A novel InGaP/GaAs camel-like field-effect transistor (HFET) has been fabricated successfully and demonstrated. Because of the use of an n/sup +/-GaAs/p/sup +/-InGaP/n-GaAs camel-like gate and GaAs/InGaAs double channel, the gate barrier height and carrier confinement are improved. Therefore, low-leakage and high-breakdown characteristics are obtained. Experimentally, this device provides high-breakdown characteristics and good device performance over a wider temperature operation range of 30-210/spl deg/C. Therefore, the studied InGaP/GaAs structure is suitable for high-power and high-temperature applications.

An interesting multiple negative-differential-resistance (NDR) phenomenon is observed in AlGaAs/InGaAs/ GaAs heterostructure bipolar transistors with abrupt or graded AlGaAs confinement layers under the inverted operation mode. The switching behaviors are mainly due to avalanche multiplication and a two-stage barrier lowering effect. The switching properties of the first S-shaped NDR observed in the device with the abrupt confinement layer are better than those observed in the device with the graded confinement layer, due to the former device's superior confinement effect on holes and electrons. The control voltage efficiency of the second S-shaped NDR is nearly equal in the studied devices because the InGaAs quantum well dominates the properties of this NDR.

A new high performance field-effect transistor using step-doped n-In0.15Ga0.85As channels was fabricated and demonstrated. For a 1 × 100 µm2 device, a high gate breakdown voltage of 15 V, a maximum drain saturation current of 735 mA/mm, a maximum transconductance of 200 mS/mm, and a wide gate voltage range > 3 V, with the transconductance > 60 mS/mm, are obtained.