J.Y. Tsai

Electrical and optical properties of beryllium-implanted Mg-doped GaN

We investigated the electrical and optical characteristics of beryllium implanted Mg-doped GaN materials. The Mg-doped GaN samples were grown by metalorganic chemical vapor deposition system and implanted with Be ions at two different energies of 50 and 150 keV and two different doses of about 1013 and 1014 cm−2. The implanted samples were subsequently rapidly thermal annealed at 900, 1000, and 1100 °C for various periods. The annealed samples showed an increase of hole concentration by three orders of magnitude from nonimplanted value of 5.5×1016 to 8.1×1019 cm−3 as obtained by Hall measurement. The high hole concentration samples also showed low specific resistance ohmic contact of about 10−3 Ω cm2 and 10−6 Ω cm2 using Ni/Au and Ni/Pd/Au metallization, respectively, without any further annealing process. It is also found from the temperature dependent photoluminescence that the activation energy of Mg dopants of the Be implanted samples has an estimated value of about 170 meV, which is nearly 30% lower ...

Investigation of beryllium implanted P-type GaN

Abstract We report the preliminary results of beryllium implanted into P-type GaN and the effects on the characteristic of Mg-doped P-GaN. These samples were implanted with Be ions were implanted with two different energies of 50 and 150 keV at two different doses of ∼10 13 and 10 14 cm −2 at room temperature. Surface morphology and photoluminescence measurements are presented.

Interface characteristics of selective tungsten on silicon using a new pretreatment technology for ULSI application

The characteristics of selective tungsten film on silicon strongly depend on the surface properties of the underlying substrate. In this work, a new pretreatment process prior to selective tungsten film deposition has been developed. A CF/sub 4//O/sub 2/ mixed plasma modification procedure and a subsequent O/sub 2/ plasma ashing step combine to achieve efficient surface precleaning. The damage and contamination induced by reactive ion etching (RIE) are thus eliminated. Concurrently, a subsequent anhydrous HF cleaning was used to remove the native oxide on silicon as well as to obtain a fluorine-passivated silicon surface which can avoid reoxidation during the transport of wafers. This new pretreatment technology produces tungsten films that retain superior physical properties within the aspects of deposition rate, film morphology, and selectivity. Also, excellent interface characteristics with low silicon consumption, low contact resistance, low contact leakage current, and fewer impurities of fluorine, oxygen, and carbon within the interfacial region are obtained.

Optical properties of InGaN quantum dots grown by SiNx nanomasks

InGaN quantum dots (QDs) deposited on SiNx nanomasks have been investigated by atomic force microscopy, photoluminescence (PL), and photoluminescence excitation (PLE) measurements. It was found that the size of QDs can be well controlled by SiNx nanomasks, enabling the manipulation of quantum confinement effect. The PL spectra of InGaN QDs contain several fine structures, and the main peaks can be attributed to families of QDs with different sizes. The emission arising from InGaN QDs and GaN buffer layer can be clearly distinguished based on PLE measurement, which can be used to improve the interpretation in the previous reports. Our study indicates that the quantum confined Stark effect due to piezoelectric field plays a very important role in the optical properties of InGaN QDs, which is very useful for the application of optoelectronic devices.

Effects of gas ratio on electrical properties of electron‐cyclotron‐resonance nitride films grown at room temperature

The effects on the electrical properties of electron‐cyclotron‐resonance (ECR) nitride films grown at room temperature with different SiH4/N2 gas ratios from 7 sccm/43 sccm to 2 sccm/48 sccm are systematically investigated. Superior properties of the films with low bulk trap density 8×1017 cm−3, small trap cross section, high breakdown strength 12.12 MV/cm, and near‐stoichiometric refractive index 2.0 are obtained when the gas ratio SiH4/N2 is 5 sccm/45 sccm, the microwave power is 210 W, and the chamber pressure is 0.5 mTorr. With the microwave power, total gas flow rate, and total pressure unchanged, the decrease in SiH4/N2 ratio lower than 5/45 results in larger trap density and some lower breakdown strength. On the other side, increasing SiH4/N2 ratio results in higher hydrogen content, lower breakdown strength, and films which are easily degraded during consecutive voltage sweep. High microwave power will eliminate the weak bonds and strengthen the electrical stability of the high SiH4/N2 ratio film.

High reflectivity distributed Bragg reflectors for 1.55 μm VCSELs using InP/airgap

Abstract A high reflecting InP/airgap distributed Bragg reflector (DBR) using InGaAs as sacrificial layers is demonstrated. The 3-pair InP/airgap DBR is formed by etching the InGaAs layers of the MOCVD grown InP/InGaAs structure using H2SO4 solution. A rigid and stable InP/airgap DBR with a peak reflectivity of 99.9% at 1.54 μm and a stopband width of about 200 nm is achieved.

Reactive Ion Pretreatment Technique to Improve the Ashing Resistance of Low Dielectric Constant High Carbon Content Polymer

The oxygen plasma via resist strip process causes significant damage to organic spin on polymer (Allied Signal X-720); thus its inter-level dielectric application is limited. A simple treatment technology, reactive glass stabilization (RGS), using reactive ion is proposed to reform the X-720 film surface. The reactive ion modification of the X-720 film can improve the resistance against oxygen plasma. The measurements of stress, thickness variation, scanning electron microscope (SEM) micrographs of gap filling and dielectric constant show that RGS can be practically used in the low dielectric material application with non-etch-back process. The measurements of fourier transform infrared (FTIR) spectroscopy, and auger electron spectroscopy (AES) show that RGS can effectively reform the surface of the X-720 film and increase the ashing resistance even in high carbon content spin on polymer.

The influence of precleaning process on the gate oxide film fabricated by electron cyclotron resonance plasma oxidation

The influence of the precleaning process on the characteristics of SiO 2 film grown by using electron cyclotron resonance (ECR) plasma oxidation at room temperature is presented in this work. We find that the growth rate, electrical properties, and reliability of the ECR plasma grown oxide is improved by this precleaning step. Two growth mechanisms are found which determine the electrical properties of the plasma grown oxide. The plasma damage is also discussed. We find that plasma oxidation produces little plasma damage in our experiments. Excellent ECR plasma grown silicon dioxide with good electrical properties and reliability characteristics are obtained by this precleaning technique.

Optically modulated internal strain in InGaN quantum dots grown on SIN x nano masks

Optically modulated internal strain has been observed in InGaN quantum dots (QDs) deposited on SiN(x) nano masks. The modulated internal strain can induce a number of intriguing effects, including the change of refractive index and the redshift of InGaN A(1)(LO) phonon. The underlying mechanism can be well accounted for in terms of the variation of internal strain through the converse piezoelectric effect arising from the screening of the internal electric field due to spatial separation of photoexcited electrons and holes. Our results point out a convenient way for the fine tuning of physical properties in nitride-based semiconductor nanostructures, which is very important for high quality optoelectronic devices.

Fabrication and characteristics of GaN-based Microcavity LEDs with high reflectivity AlN/GaN DBRs

`Abstract GaN-based micro cavity light emitting diodes (MCLEDs) which composed of 25 pairs of in-situ epitaxially grown GaN/AlN Distributed Bragg Reflector (DBR) with high reflectivity (94%), and 6 pairs ex-situ deposited SiO2/TiO2 dielectric mirrors (97.5%) was reported. The electroluminescence peak of this structure well matched with the dip of the reflectance within the stop band and the fabricated device showed excellent optical performances including the narrowed emission width (6.7 nm), and more stable emission peak wavelength (redshift free) as varying injection current density and operating temperature than the regular LED.