Ryoji Shigemasa

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.

Fabrication of 0.2 μm gate pseudomorphic inverted HEMT by phase-shifting technology

Abstract A phase-shifter edge line (PEL) mask method is applied to the gate fabrication process of InGaAs AlGaAs pseudomorphic inverted high electron mobility transistors (HEMTs). In phase-shifting technologies, the PEL mask method suits forming a fine line pattern owing to its high resolution. Mushroom shaped 0.2 μm gate pseudomorphic inverted HEMTs fabricated by using the PEL mask method show high d.c. and r.f. performances. As one of the applications of the 0.2 μm gate pseudomorphic inverted HEMTs, a decision circuit IC for 10 Gb/s optical communication systems is successfully fabricated.

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 decision circuit with phase detectors for 10 Gb/s optical communication systems

A decision circuit with a function of detecting the phase difference between the input data signal and the clock signal is presented. The novel circuit technology has been used for the phase detectors. A linear and wide-rage phase detection was achieved as well as a wide phase margin of 288/spl deg/ and a small decision ambiguity of 27 mVPP up to 10 Gb/s.