Comprehensive Study of GaAs MOSFETs Using Gadolinium Oxide and Praseodymium Oxide Layers

Abstract

The high-dielectric-constant ͑high-k͒ gadolinium oxide layer ͑Gd 2 O 3 ͒ and praseodymium oxide layer ͑Pr 2 O 3 ͒ are demonstrated as gate dielectric insulator materials in GaAs metal-oxide-semiconductor field-effect transistors ͑MOSFETs͒ using in situ high oxygen flow rate electron-beam deposition technology. The dielectric constants of the Gd 2 O 3 and Pr 2 O 3 layers developed in this study were 9.2 and 9.8, respectively. The Schottky gate turn-on voltages of GaAs MOSFETs with Gd 2 O 3 and Pr 2 O 3 insulators were 2.23 and 2.25 V, respectively, representing an improvement on the conventional p-type high electron mobility transistors ͑0.85 V͒. Moreover, the Gd 2 O 3 MOSFETs had a higher thermal stability and thermal linearity than the Pr 2 O 3 MOSFET ͑tem-perature range 100-400 K͒ due to its high binding energy, as revealed by X-ray photoelectron spectroscopy. GaAs metal-oxide-semiconductor field-effect transistors ͑MOS-FETs͒ potentially have advantages over Si-based MOSFETs for use in high-power monolithic microwave integrated circuits because of their high electron mobility and high breakdown voltage. According to previous investigations, the Schottky gate leakage current and I ds -V ds hysteresis, which are both sensitive to the interface between GaAs and the gate electrode metal, limit the device linearity.1,2 Additionally the thermally stable high-k MOSFET architecture for GaAs field-effect transistor is superior to the metal-semiconductor Schottky interface in maintaining simultaneously a high channel control ability and a low insulator leakage current. Based on the works reported by other groups, 3,4 rare-earth metal oxide high-k layers were demonstrated on GaAs MOSFET using molecular beam epitaxy ͑MBE͒ and liquid phase epitaxy. The dielectric constants of the rare-earth metal oxide high-k layers were 15-30, and these reported devices exhibited stable and reliable performance. The gate metal was deposited using an electron-beam evaporator after the high-k material growth environment for these processes, and the fixed charge in the metal-oxide interface was an additional problem. The complicated gate formation approach is also difficult to be used in high-volume industrial production. In this investigation, Pr and Gd were electron-beam evaporated with a high oxygen flow rate to produce a high-quality high-k oxide layer after the gate recess process, and then Ti/Au metal was deposited in situ in the same highvacuum chamber. This novel technology can improve the Pr and Gd oxidization ratio, which was a major drawback in our previous study. 5 The dielectric constants of Gd 2 O 3 and Pr 2 O 3 developed using this technology were 9.2 and 9.8, respectively. Accordingly, Pr 2 O 3 MOSFETs achieved a higher drain-to-source current ͑I ds ͒ and a more stable pinch-off voltage ͑V p ͒ than Gd 2 O 3 MOSFETs due to their higher dielectric constant and channel modulation ability. Furthermore, to apply these high-k GaAs MOSFETs in microwave power amplifiers, which usually generate much heat during operation, temperature-...

Stack Layer SiO[sub 2]/Gd[sub 2]O[sub 3]/SiO[sub 2]/GaAs pH-Sensitive Electrolyte Insulator Semiconductor Capacitors and Their Anneal Temperature Dependency

“…Considering the doping effect of GaAs, many rare-earth oxide ͑REO͒-based metalinsulator-semiconductor devices had been studied and reported. Different growth methods and applications have been studied, [16][17][18] and among them are the sensing devices as well. 19,20 Among those REO materials, Gd 2 O 3 had been proved to have good stability and high breakdown strength.…”