Hiroto Oda

GaAs radiation damage induced by electron cyclotron resonance plasma etching with SF6/CHF3

After SF6/CHF3 plasma exposure, the sheet resistance of Si-doped GaAs layers is higher because of carrier reduction near the surface and sputter etched surface, and this electrical and physical damage is found to depend on rf-power and µ-wave power. The carrier reduction can be almost restored by annealing at 450° C for 30 min. Exposures to He plasma or CHF3 plasma cause more extreme carrier reduction than does exposure to SF6 plasma, indicating that the carrier reduction in the damaged layers is predominantly due to the bombardment by low-mass fragments such as H and He. Low-temperature (4.2 K) photoluminescence of SF6/CHF3-plasma-exposed GaAs shows a broad and complicated spectrum (ranging from 1.25 to 1.43 eV) related to defect-complex by incorporation of hydrogen.

GaN/W/W-oxide metal base transistor with very large current gain and power gain

We demonstrate a GaN/W/W-oxide metal base transistor (MBT) whose collector is formed by oxidizing the intrinsic W base. The thickness of the nonoxidized intrinsic base of the fabricated collector-up MBT on a sapphire substrate was estimated to be 2–3 nm. Although the MBT showed large leakage, subtraction of the leakage from collector current revealed that the transistor had a very large small-signal direct current (dc) current gain of 87 dB and a dc power gain of 50 dB. This indicates that the GaN-based MBT is a possible candidate for microwave and millimeterwave amplifiers as well as for high-speed integrated circuits used in optical fiber communication system.

Damage induced by exposing AlGaAs layers to electron cyclotron resonance SF6/CHF3 plasma

We investigated the damage induced by exposing AlxGa1−xAs (x=0.30, 0.15) and GaAs layers to electron cyclotron resonance SF6/CHF3 plasma and the repair of this damage by annealing. After plasma exposure the sheet resistance of all these samples is higher because of carrier reduction near the surface. This kind of damage in AlxGa1−xAs (x=0.15) and GaAs can be restored by annealing at 450 °C for 30 min. The plasma‐damaged AlxGa1−xAs (x=0.30), however, has a further increased sheet resistance after annealing, and the sheet resistance AlxGa1−xAs (x=0.3), not exposed to the plasma is unaffected by annealing. Capacitance‐voltage measurements show that annealing causes the carrier reduction in plasma‐exposed AlxGa1−xAs (x=0.30), to extend to a greater depth.

0.2/spl mu/m Gate Aigaas/gaas Higfet (Heterostructure Insulated gate FET) with a

Summary form only given. A GaAs HIGFET with a K value of 1 A/V/sup 2//mm has been developed for application to high-speed LSIs. A description is presented of the three essential processes for fabricating this HIGFET: (1) a gate process using a

0.2μm Gate AlGaAs/GaAs HIGFETt (Heterostructure Insulated gate FET) with a (111) face of n + -GaAs selectively grown by MOCVD

A new GaAs HIGFET with K-value of 1A/V 2 /mm has been developed for application to high-speed LSIs. This paper describes three essential processes for fabricating this HIGFET: (1) a new gate process using a (111) face appearing on selectively-grown n + -GaAs, for both achieving a 0.2-μm gate and reducing the short channel effect; (2) a highly-doped GaAs channel grown by MBE, for increasing the K-value; and (3) a technique for establishing side contact between the n + -GaAs and the n-GaAs channel, for minimizing a source resistance.