Herng-Yih Ueng

Performance of High-Reliability and High-Linearity InGaP/GaAs HBT PAs for Wireless Communication

An InGaP heterojunction-bipolar-transistor (HBT) power amplifier with the best linearity and high reliability is presented in this paper for use in wireless digital mobile communication systems. We optimized the linearity of a novel HBT device and investigated its reliability. Using SILVACO software, we performed a simulation of the HBT device. The best linearity, which was revealed for the device with a capacitance ratio Cbc (0/6 V), is 1.25 at a BVceo of 22 V. After the device was fabricated, a reasonably high PAE, i.e., ~ 55%, was obtained at 2.0 GHz, and an adjacent channel power ratio of over -48 dBc was achieved. In the reliability testing, the device, which was stressed at Vce = 3 V and JC = 25 kA/cm2 under 85°C ambient temperature and 85% humidity, showed no failure for more than 1100 h. No significant beta degradation was observed under an extreme current JC = 200 kA/cm2 stress under wafer-level electrical/thermal overstress tests.

Study on annealing effects of Au thin films on Si

Abstract We report on the annealing effects of gold thin films deposited on silicon by analyzing the FTIR, AFM and d.c. conductivity, before and after annealing. FTIR spectra show higher IR transmission for samples after short time annealing, but the transmission decreases after longer annealing. The AFM photographs reveal that gold clusters are formed after short annealing and consumed by reaction with Si after longer annealing. The d.c. I–V measurement shows a nonlinear conductivity of gold thin films. The thin film resistance becomes lower after longer annealing. The I–V behavior can be explained by percolation of silicide clusters with fractal-like structures. We suggest a mechanism of silicide formation for that silicide is formed out of Au cluster and then diffused along the Si surface, which leads to less IR transmission but higher conductivity. The results of FTIR, AFM and I–V measurements are consistent with our model.

New Perspectives of Defect Physics and Defect Chemistry for Copper Ternary Chalcopyrite Semiconductors

An integrated scheme of defect physics and defect chemistry was developed to study the electronic and electrical properties of CuInSe2. We found that the Madelung energy and relaxation process play significant roles in the defect physics formulation, and some computed data of defect concentrations and the corresponding carrier concentrations using our new scheme are presented.

Preliminary steps toward industrialization of Cu-III-VI2 thin-film solar cells: development of an intelligent design tool for non-stoichiometric photovoltaic materials

Abstract In this paper, we introduce the idea of intelligent design of thin film CIGS solar cell, and we focus on the methodology of material design. We first describe in detail the calculation of the neutral defect concentrations of non-stoichiometric CuInSe 2 , CuGaSe 2 and ZnO under specific atomic chemical potential conditions ( μ x =0, x=Cu,In/Ga,Zn), and this calculation is the main procedure in the intelligent design and the key to the device design and process design. We then calculate the carrier concentrations and the electrical properties of these materials of different atomic constitutions. The main functions of this CAD tool are demonstrated.

Application of Diamond-like Carbon Film to Phase-change Optical Recording Discs

The recent development of new optical recording media is oriented toward high-density optical systems, in which data storage protection becomes very critical. Amorphous carbon films deposited by plasma-enhanced chemical vapor deposition are very smooth and possess high mass density, low friction coefficient, and very large values of hardness and elastic modulus. In this study, diamond-like carbon (DLC) film coatings on phase-change recording media are characterized using an atomic force microscope (AFM), UV-visible spectrometer and disc testers. The influence of mechanical, optical and structural properties of DLC films on the surface and spectral properties and electrical signals of discs with various DLC film thicknesses are investigated. The results of our studies indicate that DLC films indeed provide a suitable coating for protecting data stored on phase-change optical discs.

Atomic Layer Epitaxial Growth of ZnSxSe1-x on Si Substrate

High-quality undoped ZnSSe epitaxial layers are successfully grown on (100)-Si substrates by atomic layer epitaxy (ALE) in a modified low-pressure horizontal metal organic chemical vapor deposition (MOCVD) system using DMZn, H2S and H2Se as reactants at a growth temperature of 175°C and a growth pressure of 30 Torr. The vapor-solid relationship for the group VI elements are obtained experimentally. The lattice of the ZnSxSe1-x layer with sulfur content estimated to be about 93% is found to have the best lattice match to the Si substrate, as indicated by the good layer thickness uniformity, surface morphology and narrow X-ray diffraction rocking curve linewidth with a minimal FWHM of about 0.16° (570 arcsec). In addition, PL spectra exhibited a strong near-band-edge emission and weak deep-level emissions in the longer wavelength region for the epitaxial layer of ZnS0.93Se0.07. Results indicate good lattice match because of a low number of interfacial and epitaxial layer defects.

Nonlinear dc response of annealed Au thin films on Si: A random tunneling junction network model explanation

The nonlinear dc I-V behavior of gold thin film on silicon, before and after annealing, has been studied. Applying a random tunneling junction network (RTJN) model we formulate the tunneling conductivity of the thin metallic films to calculate the tunneling conductivity of cluster- and bridge junctions using our silicide formation mechanism. Our numerical result reveals good agreement with the experimental data.