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High-performance two-stage bipolar cascade 905nm vertical cavity surface emitting lasers (VCSELs) are designed and fabricated. Three different designs are investigated to compare the electrical and optical properties. Experimental results show that the current spreading and thermal problems are important factors affecting the device performance. The device with two oxide apertures accompanied with a $1.5\lambda $ -long active region spacing exhibits a very high slope efficiency of 2.27W/A and a relatively high power conversion efficiency of 52.4%. Such high-performance bipolar cascade VCSELs with 905nm are very important for LiDAR and automotive applications.

Greater than 190 °C continuous wave (CW) lasing is achieved from 905 nm high-efficiency vertical cavity surface-emitting lasers (VCSELs). The maximum power conversion efficiency (PCE) of 46.3% for ${4}~\mu \text{m}$ VCSELs was demonstrated under the ambient temperature of 30 °C. The maximum PCE decreases only 10% of its value from 30 °C to 90 °C, showing stable high-temperature characteristics. The thermal resistances and active region temperatures of the device versus ambient temperature are determined experimentally. Besides, size-dependent thermal characteristics are also analyzed by characterizing the spectral and spatial properties of devices with various apertures. It is found that the higher the ambient temperature is, the less the number of high-order modes is, and single fundamental mode operation can be realized in ${4}~\mu \text{m}$ VCSELs even at a relatively high temperature of 190 °C. The design and characterization of these high-temperature VCSEL devices might present the basis for future laser radar application.

The output characteristics of vertical cavity surface emitting lasers (VCSELs) arrays are largely influenced by temperature. We systematically studied thermal properties in 20-element oxide-confined VCSEL arrays via both theory and experiment. The output power, conversion efficiency, and threshold current dependent on ambient temperatures were measured. According to the relationship of wavelength shift and dissipated power, the device thermal resistance dependent on ambient temperature was obtained. The actual temperature in active region was successfully extracted. A 3-D heat diffusion model was established to simulate temperature distribution accurately.

Presence of phthalate metabolites (PMs) in human serum has been well documented. However, the distribution pattern of PMs in different human blood matrixes remains not well known. To investigate this, paired serum and whole blood samples were collected from 145 adults (76 males and 69 females) in Quzhou, China, and analyzed for nine PMs in this study. All PMs had high detection frequencies (70%) in human serum and whole blood, except mono benzyl phthalate. Total concentrations of detected PMs in serum and whole blood were 0.70-61 ng/mL (mean 12 ng/mL) and 1.6-33 ng/mL (7.5 ng/mL), respectively. Mono methyl phthalate (MMP), mono (2-ethylhexyl) phthalate, and mono butyl phthalate were consistently the predominant PMs in human serum and whole blood, with the mean concentrations of 3.4 and 2.0 ng/mL, 3.3 and 2.1 ng/mL, and 2.8 and 1.8 ng/mL, respectively. Females had higher mean serum concentrations of PMs, except MBP, than males. Youngest age group (20-30 years) consistently had the lowest mean whole blood levels of all PMs. For the first time, the distribution pattern of PMs in human blood was evaluated based on the calculated partitioning coefficient (K

Accumulating evidence has demonstrated the wide environmental presence of 6:2 chlorinated polyfluoroalkyl ether sulfonates (6:2 Cl-PFAES) and p-perfluorous nonenoxybenzene sulfonate (PFNOBS). However, data on the bioaccumulation and trophic magnification of these emerging poly- and perfluoroalkyl substances (PFASs) in subtropical marine environment is still limited. In this study, seawater (n = 17), sediment (n = 14), and marine organism (27 species; n = 177) samples were collected from East China Sea, and analyzed them for legacy and emerging PFASs. Besides perfluoroalkyl carboxylates and perfluorooctane sulfonate (PFOS), 6:2 Cl-PFAES was always among the predominant PFASs detected in seawater, sediment, and marine organism. For emerging PFASs, 6:2 Cl-PFAES (mean ± SD, 3.1 ± 0.17), 8:2 Cl-PFAES (3.3 ± 0.35), and PFNOBS (3.3 ± 0.19) had lower bioaccumulation factors (BAF) than PFOS (3.4 ± 0.22) in marine fish. In crab, PFNOBS (3.7 ± 0.33) had a lower biota-sediment accumulation factor (BSAF) than PFOS (3.9 ± 0.45). In snail, among all detected PFASs, PFNOBS (4.0 ± 0.42) had the highest mean log BSAF value. 8:2 Cl-PFAES consistently had a higher log BSAF value than 6:2 Cl-PFAES in snail and crab. Notably, these differences in BAF and BSAF are not significant. Among PFASs, 6:2 Cl-PFAES (2.3; 95 % confidence interval, CI: 1.9-2.6) displayed the highest trophic magnification factor (TMF). PFNOBS had the lowest TMF value (1.8, 95 % CI: 1.4-2.1), but which still indicates its weak biomagnification through the current marine food web. This is the first study reporting the bioaccumulation and biomagnification of PFNOBS in marine organisms, which deepens the understanding of its environmental behavior in the marine ecosystem.

We propose and demonstrate a photonics-based coherent dual-band radar for super-resolution range profile in this paper. This radar cannot only generate coherent dual-band linear frequency modulated signals with large bandwidths, but also realize a paralleled coherent de-chirping processing to the dual-band echoes simultaneously based on a single compact photonics-assisted transceiver. The sharing of a single transceiver for signals with different bands ensures perfect stability and coherence among the waveforms, which makes it possible to realize a super-resolution range profile by fusion of dual-band signals without heavy computation on phase compensation. In the experiment, the radar operates in S -band with a bandwidth of 1.5 GHz and X -band with a bandwidth of 3 GHz, and results show its range resolution is up to 1.6 cm by coherent fusion processing, which is nearly corresponding to the resolution gotten by a linear frequency modulated wave with a bandwidth of 9.5 GHz ranging from 2 GHz to 11.5 GHz, much higher than the scenario when the radar is operated in the single-band mode. This technology would improve the accuracy of classification and recognition of the targets.

The 808-nm vertical cavity surface emitting laser (VCSEL) with strained In0.13Ga0.75Al0.12As/Al0.3Ga0.7As quantum wells is designed and fabricated. Compared with the VCSELs with Al0.05Ga0.95As/Al0.3Ga0.7As quantum wells, the VCSEL with strained In0.13Ga0.75Al0.12As/Al0.3Ga0.7As quantum wells is demonstrated to possess higher power conversion efficiency (PCE) and better temperature stability. The maximum PCE of 43.8% for 10-μm VCSEL is achieved at an ambient temperature of 30 °C. The size-dependent thermal characteristics are also analyzed by characterizing the spectral power and output power. It demonstrates that small oxide-aperture VCSELs are advantageous for temperature-stable performance.

We demonstrate electrically controlled supermode switching and beam steering in separate-contact phased vertical cavity surface emitting laser arrays based on proton implantation. The mode switching between out-of-phase and in-phase mode was successfully achieved via controlling the injected currents. The beam steering in two directions is continuous and controllable by proper adjustment of driving currents. The properties of near-field, far-field, optical power and spectra under different currents are analyzed detailedly.

A photonic harmonic up-converter based on a self-oscillating optical frequency comb (OFC) utilizing an integrated dual-polarization dual-parallel Mach–Zehnder Modulator (DP-DPMZM) is proposed and experimentally demonstrated. One DPMZM is used to generate the optoelectronic oscillator (OEO)-based OFC, and the rest one is used to generate the optical-modulated intermediate frequency (IF) signal. Beating these two signals, the up-converted signals at different bands would be obtained. As the OFC is generated based on the OEO loop, phase noise can be very low, ensuring good phase noise properties of the up-converted signals. Moreover, frequency spacing between the combs is dependent on oscillating frequency of the OEO, which can be as large as tens of gigahertz. Thus IF signals with large bandwidth can be up-converted to RF bands without aliasing. Experimentally, the 2.5 GHz IF signal is simultaneously up-converted to 13.3, 24.1, and 34.9 GHz by a self-oscillating 7-line OFC spacing at 10.8 GHz. Owing to good phase noise property of the OEO, the up-converted signals at 13.3 and 24.1 GHz maintain the phase noise of the IF signal from 1 KHz to 100 KHz offset. The results show that the converter is promising for multi-band radar and satellite navigation applications.

We investigate the radiation effects of 1907 MeV Ta ions on the static and dynamic characteristics of 850 nm high-speed vertical cavity surface emitting lasers (VCSELs). The threshold current and slope efficiency are found to be degraded. However, appropriate ion fluence irradiation can improve the modulation bandwidth. The maximum 3 dB frequency is increased to 14.02 GHz from 13 GHz at a fluence of 1 × 108 ions/cm2. The observed behaviour can be explained in terms of reflectivity degradation of lossy distributed-Bragg reflectors as well as the degradation of quantum wells.

We demonstrate a novel photonic digital-to-analog converter (PDAC) based on a segmented architecture. The segmented PDAC is composed of compounded binary-coded and unary-coded bits, corresponding to a reduced ratio of the most significant bit to the least significant bit compared to a traditional binary PDAC. A proof-of-concept 3-bit segmented PDAC is built, which shows a greatly improved effective number of bits (ENOB) in a test frequency range of 500 MHz. A maximum ENOB of 2.94 is achieved at 400 MHz. In generating a 4-GHz linear frequency-modulated radar waveform, a gain of ~4 dB in the signal-to-noise ratio (SNR) is obtained with the novel segmented PDAC compared to that with a traditional binary PDAC.

We have investigated the dry etching of Al0.12GaAs/Al0.9GaAs Distributed Bragg Reflectors (DBRs) using photoresist mask in Inductively Coupled Plasma system with Cl2/BCl3/Ar chemistry. Resultant etch rate/etch profiles are studied as a function of ICP process parameters and photoresist mask sidewall profile. The vertical and inclined sidewalls were obtained via controlling mixing gas proportion. Enhancing physical effect in etching, photoresist mask patterns could transfer to etched substrate. In the end, controllable sidewall profile, smooth etch surface and repeatable process of Al0.12GaAs/Al0.9GaAs DBRs etching were achieved.

A photonics-based wideband distributed coherent aperture radar (DCAR) system is proposed and experimentally demonstrated. In the proposed system, the central controlling system and several spatially dispersed remote transceivers are connected by the optical fiber-based time synchronization network. In the central controlling system, the optical-carried orthogonal/coherent linear frequency modulated waveforms (LFMWs) are generated by a reconfigurable multi-channel optical arbitrary waveform generator (RMOAWG), and the signal processing for the echo waves is also implemented there. While in the remote transceivers, only the optical/RF and RF/optical conversions are carried out. Benefitting from the use of photonics-based methods, bandwidths of the generated radar signals can be large, improving the detection resolution of the system. Due to the centralized signal generation and processing, the remote transceivers can be simplified, reducing the system complexity. Moreover, the fiber-based distribution ensures low loss, good transportability, and great flexibility. Experimentally, a two-unit DCAR system operating in X-band with a bandwidth of 3 GHz is presented. When full coherence is achieved, signal-to-noise ratio (SNR) gains of 8.3 dB and 8.33 dB are obtained over a single radar for radar 1 and radar 2, respectively. Results are in good agreement with theoretical prediction. Theoretically, with such SNR gain, the range detection precision can be improved to about 2.6 times that of a single radar.

In this paper, a photonics based microwave dynamic 3D reconstruction of moving targets is proposed for the first time. The system is based on optical arbitrary waveform generation and photonics assisted 3D imaging processing. An X-band system is established experimentally. A 3D reconstruction of two pairs of cross-placement rotary balls is demonstrated to prove the effectiveness of the proposed system. Experimental results show that the proposed system can provide information on the stereoscopic physical structure of the targets dynamically, being favorable to identification and surveillance of the complex targets.

The nonlinear gain properties of GaInNAs vertical-cavity semiconductor optical amplifier operated in reflection mode are reported. A step-like differential gain and the anticlockwise bistability are predicted. The dependence of the optical bistability on the applied current and phase detuning are analyzed.

In this study, a novel submerged membrane bioreactor (SMBR) with pendulum type oscillation (PTO) hollow fiber membrane modules was developed to treat oily wastewater and control the problem of membrane fouling. To assess the potential of PTO membrane modules, the effect of oscillation orientation and frequency on membrane permeability was investigated in detail. The forces exerted on sludge flocs in the oscillating SMBR were analyzed to evaluate the impact of membrane oscillating on the cake layer resistance reduction. Results showed that the optimized PTO SMBR system exhibited 11 times higher membrane permeability and better fouling controllability than the conventional MBR system. By hydrodynamic analysis, it was found that the cooperative effect of bubble-induced turbulence and membrane oscillation in PTO SMBR system generated strong shear stress at liquid-membrane interface in vertical and horizontal direction and effectively hindered the particles from depositing on membrane surface.

W-band inverse synthetic aperture radar (ISAR) imaging systems are very useful for automatic target recognition and classification due to their high spatial resolution, high penetration and small antenna size. Broadband linear frequency modulated wave (LFMW) is usually applied to this system for its de-chirping characteristic. However, nearly all of the LFMW generated in electronic W-band ISAR system are based on multipliers and mixers, suffering seriously from electromagnetic interference (EMI) and timing jitter. And photonic-assisted LFMW generator reported before is always limited by bandwidth or time aperture. In this paper, for the first time, we propose and experimentally demonstrate a high-resolution W-band ISAR imaging system utilizing a novel logic-operation-based photonic digital-to-analog converter (LOPDAC). The equivalent sampling rate of the LOPDAC is twice as large as the rate of the digital driving signal. Thus, a broadband LFMW with a large time aperture can be generated by the LOPDAC. This LFMW is up-converted to W band with an optical frequency comb. After photonic-assisted de-chirping processing and data processing to the echo, a high-resolution two-dimension image can be obtained. Experimentally, W-band radar with a time-bandwidth product (TBWP) as large as 79200 (bandwidth 8 GHz; temporal duration 9.9 us) is established and investigated. Results show that the two-dimension (range and cross-range) imaging resolution is ~1.9 cm × ~1.6 cm with a sampling rate of 100 MSa/s in the receiver.

We present a photonics-based W-band imaging radar for non-cooperative and noncontact security check with a two-dimension imaging resolution of ∼1.9cm × ∼1.6cm and an image frame rate of 200 fps.

Anoxic/aerobic granular active carbon assisted membrane bioreactors (A/O-GAC-MBR) integrated with nanofiltration (NF)–reverse osmosis (RO) were used for leachate treatment of the Taizhou Municipal Landfill plant. In order to investigate the effect of GAC on the performance of MBR, a hybrid MBR with GAC dosed and a conventional MBR were operated in parallel. Two pilot scale MBRs showed excellent and stable removal efficiency with average above 80% for chemical oxygen demand (COD) and ammonia-nitrogen (NH 3 -N). It was noticed that the amount of high-valence metal ions were removed more than low-valence ones. By comparison, the addition of GAC not only improved the removal of hazardous organic pollutants and heavy metals, but also enhanced bioflocculation and particle size of flocs, which greatly alleviated membrane fouling. NF and RO membranes were then used for advanced treatment of MBR effluents. NF membrane exhibited excellent color removal rate of 93.75% compared to 41.82% of A/O-MBR. With the advantage of NF pretreatment, RO membrane held a steadier and higher flux as well as salt rejection than other cases reported. The final permeate from RO was proved to exceed related qualification for reutilization and can easily be recycled in industry.

Electronically controlled optical beam steering is sensitive and reliable. It is significant for phased laser radar applications. We reported the experimental characterization of three-element coherent vertical cavity surface emitting laser arrays and demonstrated two-dimensional electronical beam steering. 2-D far-field patterns, near-field patterns, and the spectra of the beam under different current conditions were measured. It is demonstrated that beam steering is continuous and predicted. Above 17.9% of the total power of the array is concentrated in the central lobe, showing high coupling efficiency. Up to a 3.26° shift angle from normal is demonstrated. The beam steering mechanism of frequency detuning between the three cavities was analyzed via both theory and experiment.

A novel combined process of Fenton oxidation, submerged membrane bioreactor (SMBR) and reverse osmosis (RO) was applied as an appropriate option for old municipal landfill leachate treatment. Fenton process was designed to intensively solve the problem of non-biodegradable organic pollutant removal and low biodegradability of leachate, although the removal of ammonia–nitrogen was similar to 10%. After SMBR treatment, it not only presented a higher removal efficiency of organics, but also exhibited high ammonia–nitrogen removal of 80% on average. The variation of extracellular polymeric substance (EPS) content, zeta potential, and particle size of flocs after Fenton effluent continually fed in SMBR was found to be benefit for alleviating membrane fouling. Finally, three kinds of RO membranes (RE, CPA, and BW) were applied to treat SMBR effluents and successfully met wastewater re-utilization requirement. Compared with simple RO process, the troublesome membrane fouling can be effectively reduced in the combined process.

We demonstrate a microwave imaging radar experimental platform, using photonic generation of linear frequency modulated waveform centered at 10GHz with 4GHz bandwidth. Distance and velocity resolution of about 5cm and 2m/s are obtained experimentally.

We apply the antenna coherence theory in order to evaluate characteristic behavior of phase-coherent VCSEL arrays. Large 19-element phase-locked VCSEL arrays with a near-diffraction-limited beam were firstly realized using proton implantation technology. The central lobe intensity is about four times that of side lobes in far-field patterns. The angular full width at half maximum (FWHM) of the far field lobes is only 1.42 degrees. A good matching between theory and experiment opens new perspectives for optimizing devices.

Electrical transport properties of a Schottky junction consisting of carbon nanotube and nitrogen-doped carbon nanotube were studied. The current-voltage characteristics of the junction exhibited reproducible rectifying behavior which could be explained by the Schottky barrier junction. The barrier height and the ideal factor were determined by fitting the current-voltage characteristics to the generalized diode equation. A near power-law dependence of I∼Vm was observed, where the exponent m increases with decreasing temperature. This effect can be accounted for by filling of deep traps at lower temperatures. The charge transport in the nanotubes is found to be strongly controlled and limited by the highly defective trap state originated from structural and chemical defects due to the doping of nitrogen in the CNx nanotube part.

A write head with submicron trackwidth was fabricated. Its main feature is to use the thickness of magnetic films to replace the stripe width of the head core as the recording trackwidth. Hard-cured photoresist was used to isolate coil from magnetic films and round off the sharp corner at the steps of bottom coil. Round steps with height ∼300 nm was shown by the scanning focused ion beam microscope images of cross section of the core. The inductance–saturation characteristic was measured by superimposing an oscillating current on a DC bias current. The experimental results of inductance do not coincide with the theoretical values. The analysis indicated that the differences are mainly originated from the leakage flux and demagnetization while the flux flowed in the magnetic circuit. The inductance curve as function of DC bias current exhibits a series of step-like discontinuities. The location and magnitude of these discontinuities are related to the shape and size of the core, and a satisfactory interpretation was given. It is believed that large saturation bias current results in that the stability of the head is insusceptible to the amplitude of signal during its operation.

A broadband photonic analog-to-digital converter (ADC) for X-band radar applications is proposed and experimentally demonstrated. An X-band signal with arbitrary waveform and a bandwidth up to 2 GHz can be synchronously sampled and processed due to the optical sampling structure. In the experiment, the chirp signal centered at 9 GHz with a bandwidth of 1.6 GHz is sampled and down-converted with a signal-to-noise ratio of 7.20 dB and an improved noise figure. Adopting the photonic ADC in the radar receiver and the above signal as the transmitted radar signal, an X-band inverse synthetic aperture radar system is set up, and the range and cross-range resolutions of 9.4 and 8.3 cm are obtained, respectively.

A photonic scheme to generate a multi-frequency phase-coded microwave signal based on a dual-output Mach-Zehnder modulator (DOMZM) and balanced detection is proposed in this paper. The DOMZM driven by an electrical coding data modulates a coherent multi-wavelength light source (CMWL), and a balanced photodetector (BPD) demodulates the output of the DOMZM; as a result, a multi-frequency phase-coded microwave signal is generated. Experiments generate two two-frequency phase-coded signals: one is 5GHz/10GHz signal with a coding rate of 2Gb/s, and the other is 10GHz/20GHz signal with a coding rate of 4Gb/s. Their autocorrelation results show a good pulse compression capability. Each frequency of a two-frequency signal has similar performances with the other in terms of peak-to-side lobe ratio (PSR) and the full width at half-maximum (FWHM) of the main lobe. The proposed scheme can be applied to radar to reduce false detections in adverse conditions. With its potential flexible frequency agility, it can be used for jamming resistance and elimination of the Doppler blind speed during moving target detection.

The fabrication of sub-0.1-/spl mu/m CMOS devices and ring oscillator circuits has been successfully explored. The key technologies include: lateral local super-steep-retrograde (SSR) channel doping with heavy ion implantation, 40-nm ultrashallow source/drain (S/D) extension, 3-nm nitrided gate oxide, dual p/sup +//n/sup +/ poly-Si gate electrode, double sidewall scheme, e-beam lithography and RIE etching for sub-0.1-/spl mu/m poly-Si gate pattern, thin and low sheet resistance SALICIDE process, etc. By these innovations in the technologies, high-performance sub-0.1-/spl mu/m CMOS devices with excellent short-channel effects (SCEs) and good driving ability have been fabricated successfully; the shortest channel length is 70 nm. 57 stage unloaded 0.1-/spl mu/m CMOS ring oscillator circuits exhibiting delay 23.8 ps/stage at 1.5 V, and 17.5 ps/stage and 12.5 ps/stage at 2 V and 3 V, respectively, are achieved.

A rotary platform is studied in this paper. The control method of its electromechanical transmission system is studied by using virtual prototype technology and control technology. Virtual prototype model of rotary platform is established in the Gear subsystem of RecurDyn, Based on the Hertz elastic contact theory. A feed-forward link and three-ring control system which are position, speed and current control link are designed in Colink. And then, the mechanical and control simulation model is set up. The response of the typical position command signal is analyzed. The simulation results show that the control method has effective engineering application, and the method can satisfy the objective of engineering control, providing a reference for the design and analysis of other electromechanical transmission control system.

Patterns and alignment of carbon nanotubes (CNTs) are particularly important for fabricating functional devices such as field emitters, scanning probes, sensors, and nanoelectronics. In this paper, the effects of various metal substrates on CNT growth are studied. Depending on the different growth mechanisms associated with the various substrate surfaces, two- or three-dimensional micropatterns of aligned carbon nanotubes have been prepared via pyrolysis of iron(II) phthalocyanine. Patterns created on silicon substrates were obtained by photolithographic techniques. The prepared CNT patterns have resolutions down to the micrometer scale. Possible growth mechanisms of aligned carbon nanotubes on different metal surfaces are also discussed.

This paper will discuss the process of T-shape gate that has been developed by direct-write electron beam lithography (EBL). The multilayer resist technique and different developing and lift-off are used to obtain a T-shape gate structure. The bottom of the "T" gate is about 100 nm. In order to realize the application of the T-shape gate in device, Heterojunction field effect transistors (HFET) have been fabricated using these T-gate structures. The extrapolated unity current gain frequency (f/sub t/) and transconductance (g/sub m/) of these transistors is 86.77 GHz and 450 ms/mm respectively.

Dielectric film on graphene severely affects the performance of graphene field-effect transistors (GFETs). The authors investigated AlN dielectric film on graphene by Raman microscopy. AlN deposition led to the appearance of disorder-related peaks and to a wider Raman-active peak. The intensities of the disorder-related modes decreased exponentially with an increase in the layer number of graphene, indicating that AlN dielectric film mainly affected the surface of graphene. According to the experimental results, the authors suggested that few-layer graphene might be a better choice than single-layer graphene for the application of GFET.

We fabricate single-walled carbon nanotube field-effect transistors (SWNT FETs) with a simple, low-cost, high-efficiency, and solution-based orientational self-assembly method. The SWNT was first functionalized with thiol groups, then suspended in an N,N-dimethylformamide solution, and finally self-assembled on predefined gold contact pads by an orientational N2 blow. A relatively high mobility of 9.2×102cm2∕Vs and an on∕off ratio greater than 105 at a bias voltage of −1V have been achieved as a result of directly covalent interaction between end-thiolated SWNT and gold contacts, which favors the fabrication of SWNT FETs as compared to the SWNT FETs bearing the similar geometry but relies on random deposition. Therefore, this orientational self-assembly approach should be a valuable tool in the mass fabrication of high-performance SWNT FETs and SWNT-based molecular-scale electronic devices.

Plasma etching with high selectivity and anisotropy for 20 nm poly-Si gate patterning on EOT of 1.4 nm gate oxynitride is developed in a Cl2/HBr/O2 gas mixture successfully. Direct write e-beam lithography is used for an SAL601 chemically amplified negative resist pattern. Using a combination of resist ashing and TEOS hard mask trimming process, sub-25 nm TEOS SiO2 mask patterns are obtained in the control. Various gas mixtures based on Cl2, HBr, and O2 have been used to study the etching characteristics of poly-Si on EOT of 1.4 nm gate oxynitride. The O2 content as well as HBr are very sensitive to etch rate, selectivity, and the protection of the sidewalls of polysilicon, owing to SiO2-like film, SiOxBry, formed on the etched surface confirmed by x-ray photoelectron spectroscopy. And the ratio of Cl2/HBr/O2 in gas mixture is also tightly related to the etching profile. Using a four-step etching process under optimum conditions the selectivity of poly-Si to oxide is much higher than 500:1, in fact, after polysilicon etching the net deposition of oxide is observed, and no damage on the active area beside the gates for EOT of 1.4 nm gate oxide is observed, too. The etching profile of the 20 nm poly-Si gate pattern is perfectly vertical and an overall narrowing by an estimated 5 nm is observed for oxide masked poly-Si gate etching. The possible mechanism is discussed. This etching process combined with resist ashing and the TEOS hard mask trimming process are implemented successfully to the fabrication of high performance 36 nm gate length complementary metal–oxide–semiconductor (CMOS) devices and 42 nm gate length 32 frequency dividers with 57 stage/201 stage CMOS ring oscillators embedded, the EOT of gate oxynitrid is 1.4 nm, and very good results are obtained.