Shih-Hsiung Chan

Optical and Electrical Characteristics of CO2-Laser-Treated Mg-Doped GaN Film

This work investigates the optical and electrical characteristics of CO 2-laser annealed Mg-doped GaN films to activate Mg-doped p-type GaN films. Results obtained from the CO 2 laser annealing investigation were similar to those of thermal annealing or low energy electron beam irradiation (LEEBI) treatment to activate the Mg-doped p-GaN films. The room-temperature photoluminescence (PL) intensity of the blue emission of the Mg-doped GaN film after 10 W laser annealing was approximately ten times stronger than that of the as-grown film. The resistivity of the Mg-doped GaN film decreased from 10 5 ˜¢cm to 2‐3˜¢cm as the laser annealing power rose above 6 W. The hole concentration of Mg-doped GaN film was approximately 1£ 10 17 cm i3 when the laser annealing power was 7.5 W.

A research on the persistent photoconductivity behavior of GaN thin films deposited by r.f. magnetron sputtering

Abstract The persistent photoconductivity (PPC) behavior has been characterized in sputtered GaN thin films using the room illumination with a wavelength of 254 nm under a 5-V bias. It was found that the N 2 partial pressure in the sputtering atmosphere has an evident effect on the PPC behavior. The obtained data show that the nitrogen vacancy is the candidate for PPC effect in the sputtered GaN film. At lower N 2 partial pressures, the nitrogen vacancy can be induced and resulted in GaN films with more donor levels as compared with those of samples deposited at higher N 2 contents. An energy band model that can account for the experimental observation of PPC behavior is proposed.

Magnesium doping of InGaAlP grown by low‐pressure metalorganic chemical vapor deposition

Bis(cyclopentadienyl) magnesium, CP2Mg, was used as a magnesium dopant in the InGaAlP layers by low‐pressure metalorganic chemical vapor deposition. The hazy surface morphology of heavily doped InGaAlP layers is significantly improved by using magnesium dopant instead of the conventional zinc dopant. We demonstrate that the effective doping efficiency of magnesium is two orders of magnitude higher than that of zinc dopant in the heavily doped InGaAlP layer grown at 720 °C.

Effects of O2 plasma treatment on the electric and dielectric characteristics of Ba0.7Sr0.3TiO3 thin films

Abstract The effects of the O2 plasma treatment on the electric and dielectric characteristics of Ba0.7Sr0.3TiO3 (BST) thin films were investigated. As a result of the exposure of the as-deposited or the annealed BST films to the O2 plasma, the leakage current density of the BST films can be improved. Typically, the leakage current density can decrease by three orders of magnitude as compared that of the non-plasma treated sample at an applied voltage of 1.5 V. It is found that the plasma treatment changes the surface morphology. The capacitance of the BST films was reduced by 10%∼30%. The improvement of the leakage current density and the reduction of a dielectric constant for the plasma treated samples could be attributed to the reduction of carbon contaminations of BST thin films. The 10 year life time of the time-dependent dielectric breakdown (TDDB) studies indicates that all the samples have a life time of over 10 years of operation at a voltage bias of 1 V.

Co-sputtered Ru-Ti alloy electrodes for DRAM applications

Abstract Co-sputtered Ru-Ti alloy films were studied for use as a bottom electrode for ferroelectric/paraelectric thin film capacitors. The Ru/Ti ratio in the alloy was found to strongly affect the resistivity, structure formation and thermal stability. The resistivity of the as-deposited films decreases and approaches that of pure Ru metal films as the amount of Ru atoms increases. From X-ray diffraction measurements, it was found that the RuTi phase has formed for the as-deposited sample. The resistivity of alloy thin films is thermally stable as the Ru composition varies from 0.68 to 0.81. It may be due to RuTiO2 formation at the surface and play an important role in preventing further oxidation of the Ru-enriched layer. This oxide also exhibits conductive behavior. On the other hand, the interface between Ru-enriched alloys and Si substrate was still sharp for the sample treated by rapid thermal processing at 600 °C for 1 min. The alloy film with high Ru composition shows excellent thermal stability and barriers against interdiffusion of Si and oxygen.

Electrical Properties of the Si Implantation in Mg Doped p-GaN

This work performs Si ion implantation to activate and convert the electrical conduction of p-GaN films from p-type to n-type. Multiple implantation method is used to form a uniform Si implanted region in the p-type GaN epitaxial layer. Implantation energies for the multiple implantation are 40, 100, and 200 keV. The implantation dose is 5 × 1015 cm2 for each implantation energy. After implantation, the samples were annealed in an N2 ambient for different annealing temperatures and annealing times. The activation efficiency reaches as high as 20% when annealing the sample at 1000 °C. The carrier activation energy is about 720 meV. The low activation energy indicates that the hopping process mechanism is the dominant mechanism for the activation of the Si implant in p-GaN. In addition, the rectifying I–V characteristic of the p–n GaN diode is also examined.

Growth and electrical characterization of Si delta‐doped GaInP by low pressure metalorganic chemical vapor deposition

The growth and electrical characterization of Si delta‐doped GaInP grown by low‐pressure metalorganic chemical vapor deposition are reported in this article. It was found that the sheet carrier density saturated as a function of doping time or flow rate. Because of the limitations of Hall‐effect measurements, the saturation was explained as the result of electron population in satellite L valley. The mobility enhancement was observed for the delta‐doped structure with an enhancement factor of 2–3. A sharp capacitance–voltage profile with a full width at half‐maximum of 30 A was obtained. Depletion‐mode Si delta‐doped GaInP field‐effect transistors with a gate length of 2 μm and gate width of 50 μm were fabricated and showed good device pinch‐off characteristics. The extrinsic maximum transconductance of 92 mS/mm was obtained and a broad plateau transconductance profile was observed to confirm the electron confinement in the V‐shape potential well of a delta‐doped GaInP layer.

Improved Output Power of 380 nm InGaN-Based LEDs Using a Heavily Mg-Doped GaN Insertion Layer Technique

High-performance InGaN-based 380 nm UV LEDs are fabricated by using a heavily Mg-doped GaN insertion layer (HD-IL) technique. Based on the transmission electron microscopy, etch pit density, and cathodoluminescence results, the HD-IL technique can substantially reduce the defect density of GaN layer. The double-crystal X-ray diffraction results are in good agreement with those observations. The internal quantum efficiency of LED sample with an HD-IL shows around 40% improvement compared with the LED sample without the use of HD-IL. When the vertical-type LED chips (size: 1 mm times 1 mm) are driven by a 350 mA current, the output powers of the LEDs with and without an HD-IL are measured to be 203.4 and 158.9 mW, respectively. As much as 28% increased light output power is achieved.

SELECTIVE EPITAXIAL-GROWTH OF GAINP BY LOW-PRESSURE METAL-ORGANIC CHEMICAL-VAPOR-DEPOSITION USING ETHYLDIMETHYLINDIUM AS IN-SOURCE

We have demonstrated the feasibility of selective epitaxial growth (SEG) of GaInP using low‐pressure metal‐organic chemical‐vapor deposition (LPMOCVD) with the combination of ethyldimethylindium (EDMIn) and triethylgallium (TEGa) as the group‐III sources. Complete selective epitaxy can be achieved at a growth temperature of 675 °C and a growth pressure of 40 Torr. The deposition of Ga‐rich polycrystalline GaInP on Si3N4 film occurs at lower temperatures. Although the incorporation efficiency of TEGa into GaInP is much lower than that of trimethylgallium, the combination of EDMIn and TEGa has been found to be a good candidate for SEG of GaInP. Low‐temperature photoluminescence shows that the selectively grown epitaxial layer has good optical quality and is useful for light emitting device applications.

Doping of InGaP epitaxial layers grown by low pressure metal-organic chemical vapor deposition

Abstract DEZn and H 2 Se were utilized as p- and n-type dopant sources for the growth in InGaP layers by low pressure metal-organic chemical vapor deposition (LP-MOCVD). The decrease in intensity of the extra spots of electron diffraction indicates that disordering is induced by the zinc doping. Streaky and wavy diffraction patterns demonstrate the formation of anti-phase domains caused by the Se dopant incorporation. The growth rate of the grown layer is reduced by more than 10% owing to the dopant incorporation. A photoluminescence emission energy difference of 141 meV between undoped and Zn-doped (5.8 × 10 18 cm −3 ) InGaP was obtained. The effects of doping on disordering, degeneracy of quasi-Fermi level and lattice constant reduction of grown layers were included in this study.