Yung Jui Chen

Ultrahigh vacuum chemically assisted ion beam etching system with a three grid ion source

A chemically assisted ion beam etching system has been developed which performs high quality, highly anisotropic etching of AlGaAs/GaAs at relatively low ion energies (200 eV). The use of three grid ion optics in a Kaufman ion source allows etching at low energies with reasonable rates without loss of profile verticality. All ultrahigh vacuum etching chamber construction with a high throughput turbomolecular pump and high vacuum loadlock provide routine high quality etching of AlGaAs without the use of etch chamber cryo panels or cryo pumps. Low ion energy and a clean vacuum environment permit the use of a single level, non hard baked photoresist mask. Benefits include high pattern resolution and fidelity, low mask erosion rate, good dimensional control, and easy, complete mask stripping as well as reduced substrate damage.

Solid source molecular beam epitaxy of low threshold 1.55 μm wavelength GaInAs/GaInAsP/InP semiconductor lasers

We report the growth and characterization of 1.55 μm wavelength GaInAsP based semiconductor lasers grown by solid source molecular beam epitaxy. Quaternary compositions were reproducible over time. Photoluminescence and x‐ray diffraction spectra indicate abrupt quantum well interfaces. Separate confinement heterostructure laser diodes with four quantum wells had threshold current densities as low as 580 A/cm2 and 275 A/cm2 for unstrained Ga0.47In0.53As and strained Ga0.27In0.73As0.8P0.2 wells, respectively. These results are as good as the best results reported for similar lasers grown by any growth technique.

Polarization insensitive 1.55-μm optical amplifier with GaAs delta-strained Ga/sub 0.47/In/sub 0.53/As quantum wells

We report a novel, polarization insensitive, 1.55-/spl mu/m semiconductor optical amplifier grown by solid source molecular beam epitaxy. The active region contains six Ga/sub 0.47/In/sub 0.53/As quantum wells, each containing three tensile strained GaAs delta layers. Simple ridge waveguide devices were fabricated with 8/spl deg/ angled facets. The internal gain is 26.5 dB for both the transverse electric and transverse magnetic polarizations at a wavelength of 1.55 /spl mu/m and an injection current of 375 mA. The polarization sensitivity of the gain is less than 1 dB for a bandwidth of 45 nm, and the gain is nearly flat with a variation of less than 1 dB for a bandwidth of 20 nm. The saturation output power of these devices is 11 dBm. These results are reproducible and comparable to reports from more complex device designs.

Etch‐mask of pyrolytic‐photoresist thin‐film for self‐aligned fabrication of smooth and deep faceted three‐dimensional microstructures

Etch‐mask thin‐film material that is particulate‐free and topographically smooth has been created from a standard photoresist spun onto standard semiconductor substrates such as gallium arsenide, indium phosphide, and silicon, and then pyrolyzed by exposing to a temperature of 300 °C in air atmosphere for 1 min on a standard laboratory hot‐plate. The resulting pyrolytic‐photoresist thin‐film is chemically inert to many standard organic solvents including the solvent of photoresist itself and to many inorganic reagents used in semiconductor processing. Therefore the pyrolytic‐photoresist can be patterned by sulfur hexafluoride reactive ion etching via a standard photoresist mask. Upon stripping the standard photoresist in a mixture of 1:1/acetone:developer agitated ultrasonically, the remaining patterned pyrolytic‐photoresist performs as an excellent etch‐mask in chemically assisted ion beam etching and reactive ion etching systems. Thus it can be a key material in the multilayer masking technique used to ...

Air-bridges, air-ramps, planarization, and encapsulation using pyrolytic photoresist in the fabrication of three-dimensional microstructures

Pyrolyzation of photolithographically patterned photoresist on semiconductor substrates such as silicon, gallium arsenide, and indium phosphide, results in a convex-shaped, chemically inert, temporary form that functions as a mold upon which to lift-off evaporated thin films such as metals. The pyrolyzation process is simply a bake on a standard laboratory hot-plate that is ramped from room temperature to 300 °C air. The pyrolytic-photoresist form is subsequently removed in an oxygen plasma stripper leaving behind the three-dimensional lifted off thin films of free-standing, convex-shaped, full-arch air-bridges or half-arch air-bridges that we call air-ramps. Some applications are interconnects for high-speed devices; inter-level interconnects; out-of-plane coils for out-of-plane inductors; microdomes for eletromagnetic shielding; electrodes for field-emitter tips; and microelectromechanical structures. Pyrolyzing photoresist does not alter the good planarization capabilities of photoresist. Because pyrol...

Reflectivity and photoluminescence spectra of GaAs quantum wells in a magnetic field

Abstract We present photoluminescence and reflectance spectra of GaAs/Al x Ga 1− x As quantum wells in a magnetic field for the Faraday geometry. The photoluminescence peaks recorded are among the most intense and narrow reported to date. This has allowed us to study the behavior of closely spaced bound exciton lines under a magnetic field. Several new features including magnetic field induced splitting of the bound exciton emission peaks are reported.

Bound Exciton Induced Photoluminescence Linewidth Broadening in GaAs Quantum Wells

The linewidth of the free exciton photoluminescence peak has been observed to broaden when the sample is excited by light whose energy exceeds the bandgap of the barrier. The net photoluminescence efficiency as well as the width of the free exciton line is observed to depend on the lattice temperature as well as the excitation wavelength and intensity. This is attributed to the scattering of free excitons by the charges trapped in the

Wet-chemistry surface treatment for dark-current reduction that preserves lateral dimensions of reactive ion etched Ga/sub 0.47/In/sub 0.53/As p-i-n diode photodetectors

Al_xGa _{1-x} As

InGaAs/InP p-i-n heterostructure photodiode arrays on AlGaAs/GaAs waveguide films by solid source molecular beam epitaxy

barrier.

Intrinsic and extrinsic processes in photoluminescence, reflectivity, and spin dynamics of GaAs quantum wells

A wet-chemistry treatment, consisting of a fresh mixture of one-to-one 2-propanol plus concentrated sulfuric acid added to photoresist developer, which is tetramethyl ammonium hydroxide, was found to reduce the dark-current density at the -5-V dc reverse-bias to 2 pA//spl mu/m/sup 2/ (2/spl times/10/sup -4/ A/cm/sup 2/), and simultaneously to maintain the lateral geometrical dimensions, of reactive ion etched, 3 micrometer tall, right-cylinder mesa, Ga/sub 0.47/In/sub 0.53/As p-i-n diode photodetectors with diameters of 100, 50, and 25 /spl mu/m.