Tamotsu Kimura

Gate Orientation Dependence of InGaAs/AlGaAs High Electron Mobility Transistors Formed by Wet Recess Etching

The gate orientation dependence of InGaAs/AlGaAs high electron mobility transistors (HEMTs) formed by the wet-chemical recess etching has been evaluated. The short channel effect strongly depends on the gate orientation and is significant in the order of [011], [001] and [011] oriented devices. Such orientation dependence results from a difference of the side-etching lengths, which are 0.01 µm, 0.03 µm and 0.06 µm for the [011], [001] and [011] oriented devices, respectively. The other characteristics of HEMTs such BVgd, gm and fT also depend on the gate orientation because of a difference of the recessed shape.

Schottky Characteristics of Subhalf-Micron Gate GaAs Metal-Semiconductor Field-Effect Transistor

This paper describes Schottky characteristics of the subhalf-micron W-Al gate GaAs metal-semiconductor field-effect transistor (MESFET), which is fabricated using the phase-shifting mask technology. We observed that Schottky characteristics depend on the gate length and gate direction especially in the subhalf-micron range. This phenomena is caused by the piezoelectric effect; however, the degree of the barrier height shift is small compared to that of the threshold voltage, and this can be explained by the depth profile of the induced charges under the gate of subhalf micron.

Schottky Characteristics of InAlAs Grown by Metal-Organic Chemical Vapor Deposition

Schottky characteristics of InAlAs grown by metal-organic chemical vapor deposition (MOCVD) have been evaluated. InAlAs Schottky characteristics are strongly affected by MOCVD growth temperature. The reverse current of InAlAs grown at 700°C is more than one order of magnitude larger than that at 750°C. From deep-level transient spectroscopy (DLTS) measurements, electron traps with activation energies of 0.45, 0.33 and 0.15 eV have been observed in InAlAs grown at 700°C. The results of C-V, Hall and secondary ion mass spectrometry (SIMS) measurements suggest that the trap is acceptor-type and seems to be related not to impurities but to intrinsic defects. The mechanism of the large reverse current in InAlAs grown at 700°C is believed to be due to the conduction through the trap.

Electron irradiation during Schottky gate metal evaporation and its effect on the stability of InGaAs/AlGaAs HEMTs

Abstract The threshold voltage of InGaAs/AlGaAs HEMTs with molybdenum Schottky gate were observed to shift after a high forward gate current test. Experimental results show that this phenomenon is characteristic of molybdenum Schottky gates on GaAs, and it is related to the deep traps near the interface between molybdenum (Mo) and GaAs or within the semiconductor to the depth of 1000A. Such deep traps were introduced because of the electron irradiation effect during the electron beam deposition of Mo on GaAs. Insertion of a Ti layer thicker than 100Abetween Mo and GaAs was found to be effective for suppressing the shift by the blocking effect for the electron irradiation.

Shift in Threshold Voltage and Schottky Barrier Height of Molybdenum Gate Gallium Arsenide Field Effect Transistors after High Forward Gate Current Test

The threshold voltage and the Schottky barrier height of InGaAs/AlGaAs HEMTs or GaAs MESFETs with molybdenum Schottky gates were observed to shift after high forward gate current tests, and the shift was recovered by subsequent heat treatment. Experimental results show that this phenomenon is characteristic of molybdenum Schottky gates on GaAs, and it is related to the deep traps near the interface between molybdenum and GaAs or within the GaAs channel layer. Such deep traps were introduced due to the electron irradiation effect during the electron beam deposition of the molybdenum (Mo) on GaAs. Insertion of a thin Ti layer between Mo and GaAs was found to be effective for suppressing the shift.

A study of GaAs digital ICs on Si substrates

The speed characteristics and the sidegating effect of GaAs metal semiconductor field effect transistors (MESFETs) on Si substrates were studied. The propagation delay of a direct-coupled FET logic (DCFL) inverter with 0.3-μm-gate MESFETs was 19.9 ps/gate, which was about 19.9 ps/gate larger than that for the inverter on undoped liquid-encapsulated Czochralski (LEC) semi-insulating GaAs substrates. As for the sidegating effect, devices on the GaAs on Si (GaAs/Si) substrates showed a smaller decrease in drain current than those on GaAs substrates as side-gate voltage increased

Evaluation of Effective Gate Length of Gallium Arsenide Metal-Semiconductor Field Effect Transistors.

To improve the performance of field-effect transistors (FETs), it is necessary to reduce the gate length. However the gate length, which affects the characteristics of FETs, is generally not the same as the metallurgical gate length, and is referred to as the effective gate length, which depends on the device structure. This paper describes a method of evaluating the effective gate length of GaAs MESFETs using I–V measurement under the bias condition, then discusses the relationship between the effective gate length and the structural parameters of the device, such as the distance between the gate metal and the n+ region, which is controlled by the sidewall thickness for n+ self-alignment ion implantation. From the results of a two-dimensional device simulation, it is observed that the effective gate length is related to the depletion layer extending around the gate electrode.