Hyung-Sup Yoon

Ultra low noise characteristics of AlGaAs/InGaAs/GaAs pseudomorphic HEMT's with wide head T-shaped gate

The fully passivated low noise AlGaAs/InGaAs/GaAs pseudomorphic (PM) HEMT with 0.13 /spl mu/m T-shaped gate was fabricated using dose split electron beam lithography method (DSM). This device exhibited low noise figures of 0.31 and 0.45 dB at 12 and 18 GHz, respectively. These noise figures are the lowest value ever reported for the GaAs based HEMTs. These results are attributed to the extremely low gate resistance which results from wide head T-shaped gate having the higher ratio more than 10 of gate head length to gate footprint.

Low-frequency noise characteristics of metamorphic In0.52Al0.48As/In0.60Ga0.40As double-heterostructure pseudomorphic high electron mobility transistors grown on a GaAs substrate

Abstract Low-frequency noise characteristics of metamorphic In0.52Al0.48As/In0.60Ga0.40As double-heterostructure pseudomorphic high electron mobility transistors (p-HEMTs) grown on a GaAs substrate are investigated. Low-frequency noise spectral density of the In0.52Al0.48As/In0.60Ga0.40As metamorphic HEMT (MM-HEMT) having two 0.5×50 μm2 gates was measured for temperatures between 200 and 400 K and frequencies between 1 Hz and 53 kHz. Dependence of input noise spectral density on gate–source and drain–source bias voltages and transconductance frequency dispersion characteristics were also characterized. The low-frequency input noise spectra of the MM-HEMT showed pure 1/f noise characteristics for the temperature and the frequency ranges investigated, indicating that there exists insignificant level of deep traps associated with the metamorphic epitaxial layer growth. The MM-HEMT showed a very low-noise spectral density (0.8×10−13 V2/Hz at 1 kHz) and the Hooge parameter (3.7×10−5) that are comparable to those of the state-of-the-art In0.52Al0.48As/In0.53Ga0.47As HEMT grown on an InP substrate and an extremely small transconductance frequency dispersion (Δgm/gm0

Room temperature photoluminescence studies of δ-doped pseudomorphic high electron mobility transistor AlGaAs/InGaAs/GaAs structures

Abstract We report the room temperature characteristics of photoluminescence emission in δ-doped pseudomorphic high electron mobility transistor AlGaAs/InGaAs/GaAs structures. A theoretical self-consistent calculation of band structure demonstrates that dominant emissions are due to the transition from the second electron subband to the first heavy hole subband, namely, (e2-hh1). The calculation also predicts that along with the increase of the δ-doping level, the transition energies shift to lower energies. It is explained as band gap renormalization caused by change of confined levels by band bending and electrostatic attraction. The numerical fits to calculated transition energies show that (e2-hh1) obeys an eponential decay change and (e1-hh1) decreases linearly along with the increase of δ-doping level.

Very low noise characteristics of AlGaAs/InGaAs HEMTs with wide head T-gate

The parasitic gate resistance is one of the most important factors in determining the noise performance of HEMTs. In order to reduce the gate resistance, T-shaped gates with large cross-sectional area are required. In this study, we report a AlGaAs/InGaAs pseudomorphic HEMT with a newly developed wide head T-gate fabricated by using dose split electron beam lithography and selective gate recess etching.