A double L-shaped heat pipe sink that uses a micro heat pipe array is proposed for heat dissipation and temperature uniformity in high-power electronics chip cooling for the first time in this work. The radiator is composed of two L-shaped micro heat pipe arrays filled with copper foam wick (the composite wick structure) and aluminum flat fins, which can reduce the temperature of hotspots of electronics effectively and has good inclination adaptability. Through experiments, the heat transfer performance is studied under different copper foam filling lengths, liquid filling rates, and inclination angles. Then, a numerical simulation of the effect of different fin parameters on the radiator is conducted using Icepak. The composite wick structure effectively enhances the heat transfer capability of the radiator. Results show that the average thermal resistance of the micro heat pipe array with a composite wick structure is 0.258 K/W, indicating a 23 % reduction compared with that of a single wick structure double L shape heat pipe sink. The double L shape heat pipe sink solves the phenomenon of chip temperature jump caused by the hotspots of high heat flux. The average temperature of the chip surface can be controlled below 62 degrees C when the localized heat flux is 200 W/cm2. Simulation results show that optimization of the fin structure can stabilize the temperature of the 214 W chip at 70.1 degrees C, which is reduced by 8.7 % than before optimization.

We achieve 13.5 mW optical output power, 48% power conversion efficiency, 1.17 W/A slope efficiency and 17 kW/cm2 laser power density with top-surface-emitting 940 nm oxide-confined vertical-cavity surface-emitting laser (VCSEL). The physical mechanism of minimum threshold current generation in oxide-confined VCSEL has been thoroughly studied theoretically and experimentally. Further, we also succeeded in 90.8 mW optical output power, 40% power conversion efficiency with 2 × 4 VCSEL arrays. We find an increase in output power and PCE of 2 × 2 VCSEL arrays as we increase the array spacing which we attribute primarily to increased heat dissipation and reduced thermal crosstalk between the emitters. Thermal properties in oxide-confined 2 × 2 VCSEL arrays were analyzed numerically and experimentally. The simulated results are in good agreement with the measurement. It is proved that theoretical simulation is very useful for the future device optimization.

For the past years, ArF immersion has been employed as the major lithography tool in the foundry manufacturing to fabricate the patterns of minimum pitch and size. However, for semiconductor scaling beyond N7 the application of EUV lithography is considered to be crucially important to overcome the physical limitation of ArF immersion and to realize even smaller patterns. In the case of ArF photo processes, the best mask size for a specific pitch could be selected with the consideration of optical performances such as NILS, MEEF, etc. In contrast, for the EUV processes the optical and resist stochastic effect should also be taken into account as an important factor in deciding the best mask size. In this paper, we are going to discuss the dose and mask size optimization process for an DRAM contact hole layer with EUV lithography utilizing stochastic simulations; this contains also the stochastic response of the resist. In order to calibrate a predictive stochastic resist model, which is required for this application, measurements of the stochastic resist response are necessary. In addition, the systematic and stochastic errors of CD-SEM measurements have to be estimated. We will compare experimentally obtained NILS and MEEF to simulated results, which are in very good agreement. Also, we show a comparison of experimental and computational analysis of LCDU (Local CD Uniformity).

In this paper,the isolation ring structure of Si-based PIN photodetector was studied by discussing the relationship between the isolation ring and dark curent.Simulations and test analysis were carried out.The isolation ring reduces the dark current by isolating the active region from the edge.Combining the simulation results with the experimental results,it shows that the isolation ring mainly reduces the dark current related with the circumference,and the effect is more obvious on small-size devices.

Vertical-cavity surface-emitting lasers (VCSEL) are widely used in short-reach optical communication links and interconnects because of their low energy consumption,low threshold current,and high modulation speed.Wet etching and dry etching are two processes for high-speed VCSEL fabrication of mesa structure,which will influence the size of oxide layer.In this paper,the impact of the oxide layer on the parasitic capacitance is analyzed.Compared to the wet etching process,the oxide capacitance of 7 μm oxidized aperture VCSEL is reduced from 902.23 fF to 581.32 fF,and the capacitance associated with the intrinsic region is also reduced from 320.72 fF to 206.65 fF.The small-signal modulation response of high-speed VCSEL with GaAs quantum wells fabricated by wet and dry etching process were measured respectively,and the bandwidth of 7 μm oxide aperture VCSEL with dry etching was increased to 16.1 GHz.

A two-dimensional apodized grating coupler for interfacing between single-mode fiber and photonic circuit is demonstrated in order to bridge the mode gap between the grating coupler and optical fiber. The grating grooves of the grating couplers are realized by columns of fully etched nanostructures, which are utilized to digitally tailor the effective refractive index of each groove in order to obtain the Gaussian-like output diffractive mode and then enhance the coupling efficiency. Compared with that of the uniform grating coupler, the coupling efficiency of the apodized grating coupler is increased by 4.3% and 5.7%, respectively, for the nanoholes and nanorectangles as refractive index tunes layer.

Polarization-stable 980nm oxide-confined vertical-cavity surface-emitting lasers with 3 μm diamond-shaped aperture are fabricated by comprehensively utilizing the anisotropic properties of wet etching and wet nitrogen oxidation of III–V semiconductor materials. Polarization-stable operation along the major axis of the diamond-shaped oxide aperture with 11 dB orthogonal polarization suppression ratio is achieved in a temperature range of 15–55°C from the threshold to 4 mA.

Two-dimensional apodized grating couplers are proposed with grating grooves realized by a series of nano-rectangles, with the feasibility of digital tailoring the equivalent refractive index of each groove in order to obtain the Gaussian output diffractive mode in order to enhance the coupling efficiency to the optical fiber. According to the requirement of leakage factor distribution for a Gaussian output profile, the corresponding effective refractive index of the grating groove, duty cycle, and period are designed according to the equivalent medium theory. The peak coupling efficiency of 93.1% at 1550 nm and 3 dB bandwidth of 82 nm are achieved.

The maximum power conversion efficiencies of the top-emitting,oxide-confined,two-dimensional integrated 2×2 and4×4 vertical-cavity surface-emitting laser（VCSEL） arrays with the oxide-apertures of 6 μm,16 μm,19 μm,26 μm,29 μm,36 μm,39 μm,and 46 urn are fabricated and characterized,respectively.The maximum power conversion efficiencies increase rapidly with the augment of oxide-aperture at the beginning and then decrease slowly.A maximum value of27.91%at an oxide-aperture of 18.6 μm is achieved by simulation.The experimental data are well consistent with the simulation results,which are analyzed by utilizing an empirical model.

Heterojunction planar Gunn devices were first demonstrated by Khalid et al in 2007. This new design of Gunn device, or transferred electron device, was based on the well-established material system of GaAs as the oscillation media. The design did not only breakthrough the frequency record of GaAs for conventional Gunn devices, but also has several advantages over conventional Gunn devices, such as the possibility of making multiple oscillators on a single chip and compatibility with monolithic integrated circuits. However, these devices faced the challenge of producing high enough RF power for practical applications and circuit technology for integration. This thesis describes systematic work on the design and characterisations of planar Gunn diodes and the associated millimetre-wave circuits for RF signal power enhancement. Focus has been put on improving the design of planar Gunn diodes and developing high performance integrated millimetre-wave circuits for combining multiple Gunn diodes. Improvement of device design has been proved to be one of the key methods to increase the signal power. By introducing additional δ-doping layers, electron concentration in the channel increases and better Gunn domain formation is achieved, therefore higher RF power and frequency are produced. Combining multiple channels in the vertical direction within devices is another effective way to increase the output signal power as well as DC-to-RF conversion efficiency. In addition, an alternative material system, i.e. In0.23Ga0.77As, has also been studied for this purpose. Planar passive components, such as resonators, couplers, low pass filters (LPFs), and power combiners with high performance over 100 GHz have been developed. These components can be smoothly integrated with planar Gunn diodes for compact planar Gunn oscillators, and therefore contribute to RF power enhancement. In addition, several new measurement techniques for characterising oscillators and passive devices have also been developed during this work and will be included in this thesis.