A Comparative Study of a Dielectric-Defined Process on AlGaAs/InGaAs/GaAs PHEMTs

Abstract

We report on the fabrication of an AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) using a dielectric‐defined process. This process was utilized to fabricate 0.12 μm × 100 µm T‐gate PHEMTs. A two‐step etch process was performed to define the gate footprint in the SiNx. The SiNx was etched either by dry etching alone or using a combination of wet and dry etching. The gate recessing was done in three steps: a wet etching for removal of the damaged surface layer, a dry etching for the narrow recess, and wet etching. A structure for the top of the T‐gate consisting of a wide head part and a narrow lower layer part has been employed, taking advantage of the large cross‐sectional area of the gate and its mechanically stable structure. From s‐parameter data of up to 50 GHz, an extrapolated cut‐off frequency of as high as 104 GHz was obtained. When comparing sample C (combination of wet and dry etching for the SiNx) with sample A (dry etching for the SiNx), we observed an 62.5% increase of the cut‐off frequency. This is believed to be due to considerable decreases of the gate‐source and gate‐drain capacitances. This improvement in RF performance can be understood in terms of the decrease in parasitic capacitances, which is due to the use of the dielectric and the gate recess etching method.

Integrated microHall magnetometer to measure the magnetic properties of nanoparticles

“…High mobility wafers were custom-grown (Electronics and Telecommunications Research Institute, Korea) via molecular beam epitaxy on a semi-insulating GaAs substrate 33 . Following layers were formed: 5000 Å GaAs buffer, 30 periods of the AlGaAs/GaAs superlattices, an undoped Al 0.23 Ga 0.77 As buffer, silicon planar doping (1 × 10 12 cm −2 ), a 20 Å Al 0.23 Ga 0.77 As spacer, a 120 Å In 0.2 Ga 0.8 As channel, a 35 Å Al 0.23 Ga 0.77 As spacer, silicon planar doping (4.5 × 10 12 cm −2 ), and a 250 Å Al 0.23 Ga 0.77 As Schottky contact layer.…”

Aperture-Miniaturized Antenna Loaded with Split Ring Resonator Array

“…The 0.5 µm GaAs process of ETRI [3], [7] was used to fabricate the SPDT Tx/Rx MMIC switches. The measured DC characteristics and extracted C on and C off from the fabricated pHEMTs were in good agreement with the calculations.…”

“…The measured DC characteristics and extracted C on and C off from the fabricated pHEMTs were in good agreement with the calculations. The 0.5 µm GaAs process of ETRI [3], [7] was used to fabricate the SPDT Tx/Rx MMIC switches. For the circuit design of the SPDT MMIC switches, we used a switch transistor with a 400 μm gate periphery for each path and a shunt-series circuit configuration that is widely used in 2.4 GHz and 5.8 GHz wireless local area network system applications.…”

Comparative Study of DC and Microwave Characteristics of 0.12 µm Double-Recessed Gate AlGaAs/InGaAs/GaAs Pseudomorphic High-Electron-Mobility Transistors Using Dielectric-Assisted Process

“…In order to reduce the gate resistance, T-shaped gates with large cross-sectional areas are required. [8][9][10] Their fabrication can be either based on electron beam lithography (EBL) with multiple resist layers [11][12][13] or on optical stepper lithography combined with sidewall spacers. 14) The shape of the T-gate, the gate footprint length L g , as well as the thickness of the passivation all have a major impact on the gate capacitance C gs which is a key parameter determining the RF performance of the device.…”