Yen-Ku Lin

AlGaN/GaN HEMTs With Damage-Free Neutral Beam Etched Gate Recess for High-Performance Millimeter-Wave Applications

The electrical performances of gate-recessed AlGaN/GaN high-electron mobility transistors (HEMTs) fabricated using the damage-free neutral beam etching (NBE) method are demonstrated. The NBE method could eliminate the plasma-induced defects generated by irradiating ultraviolet/VUV photons in the conventional inductively coupled plasma reactive ion etching method. The AlGaN/GaN HEMT device fabricated using the new gate recess process exhibited superior electrical performances, including a maximum drain current density (IDS,max) of 1.54 A/mm, low 1/f noise, a current-gain cutoff frequency (fT) of 153 GHz, a maximum frequency of oscillation (fMAX) of 167 GHz, and a minimum noise figure (NFmin) of 3.28 dB with an associated gain (GAS) of 5.06 dB at 54 GHz. Such superior characteristics confirm the inherent advantages of adopting the damage-free NBE process in fabricating GaN devices for millimeter-wave applications.

Broadband antireflection sub-wavelength structure of InGaP/InGaAs/Ge triple junction solar cell with composition-graded SiNx

This work reports a fabrication strategy to improve the antireflective ability of a InGaP/GaAs/Ge triple-junction solar cell, by combining a nano-templating technique and a chemical-synthesis approach. SiH4 and N2 were used as ammonia-free reaction gases in a plasma-enhanced chemical vapor deposition (PECVD) to prepare Si3N4 as an original antireflective coating (ARC) layer with better chemical stability. Composition-graded SiNx was successfully integrated with sub-wavelength structure by modulating SiH4/N2 ratio during PECVD deposition, and followed by a controllable gold-nanoparticle masking technique on top of the solar cell. Finite-difference time-domain solution was employed to simulate and optimize the aspect-ratio of the ARC, under the condition of variable refractive index over a broad wavelength window, and followed by the masking technique to obtain the desired ARC dimension. This enabled a low light reflectance (<10%) over a broad spectral bandwidth (300–1800 nm) for the solar cell with excellent stability, because of the triple advantages of structural optimization, better chemical stability and graded refractive index of the ARC. The solar cells performance was tested and showed great competitiveness to those of forefront studies, suggesting the feasibility of the proposed technology.

Electrical Analysis and PBTI Reliability of In 0.53 Ga 0.47 As MOSFETs With AlN Passivation Layer and NH 3 Postremote Plasma Treatment

We report a notable improvement in performance, electron transport, and reliability of HfO₂/In_0.53Ga_0.47As nMOSFETs using a plasma-enhanced atomic layer deposition AlN interfacial passivation layer (IPL) and NH₃ postremote plasma treatment (PRPT). The interface state density D_it decreased by approximately one order of magnitude from 6.1×10¹² to 4×10¹¹ cm^-2eV^-1, and the border trap density Nbt also declined ten times from 2.8×10¹⁹ to 2.7×10¹⁸ cm^-3, resulting in the reduction of the accumulation frequency dispersion and eliminate the inversion hump in C-V characteristics, and thus improves the device performances. Furthermore, positive bias temperature instability stress indicates that the sample with the AlN IPL and NH₃ PRPT is more reliable than the sample without any IPL and plasma treatment. During PBT stress, a smaller threshold voltage shift and less transconductance degradation were observed for the sample with the AlN IPL and NH₃ PRPT. In addition, the maximum overdrive voltage for a ten-year operating lifetime increased from 0.19 to 0.41 V.

AlGaN/GaN HEMTs With Damage-Free Neutral Beam Etched Gate Recess for High-Performance Millimeter-Wave Applications (vol 37, pg 1395, 2016)

In the above paper [1] , the first footnote should have included the following information.

Enhancement-mode AlGaN/GaN MIS-HEMTs with low threshold voltage hysteresis using damage-free neutral beam etched gate recess

An enhancement-mode AlGaN/GaN MIS-HEMTs with low threshold voltage hysteresis using damage-free neutral beam etched (NBE) gate recess is reported. The NBE can eliminate the plasma-induced defects that generated by irradiating UV/VUV photons as encounted in the conventional inductively coupled plasma-reactive-ion etching (ICP-RIE). Combining the new gate recess process and PEALD-AlN interfacial passivation layer, the Al2O3/AlGaN/GaN enhancement-mode HEMT device shows a threshold voltage of 1.5 V and a current density of 449 mA/mm, and the three-terminal breakdown voltage was 432 V. The device also shows small hysteresis in threshold voltage at stable I-V curve.