Y. Feng

Band‐gap tuning of InGaAs/InGaAsP/InP laser using high energy ion implantation

The technique of ion‐induced quantum well intermixing using broad area, high energy (1 MeV P+) ion implantation has been used to tune the emission wavelength of an InGaAs/InGaAsP/InP multiple quantum well (MQW) laser operating at 1.5 μm. The optical quality of the band‐gap shifted material is assessed using low‐temperature photoluminescence (PL). The band‐gap tuned lasers are characterized in terms of threshold current density and external quantum efficiency and exhibit blue shifts in the lasing spectra of up to 63 nm. This approach offers the prospect of a powerful and relatively simple fabrication technique for integrating active as well as passive optoelectronic devices.

Polarization insensitive InGaAs/InGaAsP/InP amplifiers using quantum well intermixing

A polarization insensitive optical amplifier based on a lattice matched InGaAs/InGaAsP/InP multiple quantum well (MQW) laser structure operating at 1.5 μm has been fabricated through vacancy enhanced quantum well intermixing using broad area, high energy (1 MeV P+) ion implantation. A simple model shows that if the interdiffusion rate of the anions is larger than that of the cations, the blue shift in the ground state heavy hole transition energy after implantation and annealing is greater than the light hole state blue shift, bringing the two bands together. Current–voltage measurements indicate that junction characteristics are well maintained after implantation. This simple technique for fabricating polarization insensitive optical amplifiers is readily extended to the monolithical integration of such devices along with other passive and active optoelectronic devices and opens the door to practical photonic integrated circuits.

HIGH-RELIABILITY BLUE-SHIFTED INGAASP/INP LASERS

InGaAsP/InP quantum well (QW) ridge waveguide lasers emitting nominally at 1310 nm have been ‘‘blue‐shifted’’ selectively (as much as 70 nm) on a full 50‐mm‐diameter wafer after growth. P+ ion implantation at 1 MeV, 200 °C through a variable thickness SiO2 mask was used to induce various degrees of QW intermixing after postimplantation annealing at 700 °C. Irrespective of the amount of intermixing induced (blue shift), all fabricated devices exhibited 20–25 mA lasing threshold current and 0.25–0.30 W/A differential quantum efficiency. Device reliability was equivalent to standard (nonimplanted) lasers when the wavelength shift was 35 nm or less, corresponding to predicted lifetime in excess of 25 years while operating cw at 25 °C. The performance and reliability data clearly indicate that the concentration of residual defects introduced in the active region by the implantation/annealing process is negligibly small. The present results, which are a product of a straightforward fabrication process, suggest ...

The fabrication of a broad-spectrum light-emitting diode using high-energy ion implantation

High-energy ion implantation is used to spatially modify the bandgap of a 1.5-/spl mu/m laser structure to fabricate a broad spectrum light emitting diode (LED). An increase in the emission full width half maximum (FWHM) from 28 nm to 90 nm is observed. An absorbing section at one end of the device is used to suppress lasing operation and remove Fabry-Perot noise.

Lateral selectivity of ion-induced quantum well intermixing

Quantum well (QW) intermixing using high-energy ion implantation is a promising technique for laterally selective, post-growth modification of a quantum well structure. In this work, we investigate the lateral selectivity of the technique, which is a function of the ion straggling during implantation and of the lateral diffusion of defects during post-implantation annealing. We have used photoluminescence and a specially designed mask to monitor the intermixing of QWs under masked regions. A significant amount of intermixing, resulting in a blueshift of the QW band-gap energy, was observed when the mask stripe width was less than 5 μm, thus giving a lateral selectivity of 2.5 μm.

Polarization-insensitive quantum well optoelectronic devices using quantum well shape modification

Polarization insensitive 1.5 micrometer QW optical amplifiers, modulators, and detectors were fabricated using a novel, simple, post-growth, integratable technique. The process utilizes ion-implantation-induced, spatially selective, quantum well (QW) shape modification. A simple model shows that if the interdiffusion rate of the anions is larger than that of the cations, the blue shift in the ground state heavy hole transition energy after implantation and annealing is greater than the light hole state blue shift, merging the two bands and thus eliminating the difference between the TE (transverse electric) and TM (transverse magnetic) waveguide propagation modes. Current- voltage measurements indicate that junction characteristics are well maintained after processing. This simple technique for fabricating discrete polarization insensitive optoelectronic devices is readily extended to the monolithic integration of such devices along with other passive and active optoelectronic devices and provides a pathway to practical photonic integrated circuits.

Quantum well intermixing for the realization of photonic integrated circuits

A technique, based on quantum well (QW) intermixing, has been developed for the post growth, spatially selective tuning of the QW bandgap in a laser structure. High energy (MeV) ion implantation is used to create a large number of vacancies and interstitials in the device. During high temperature processing, these defects simultaneously enhance the intermixing of the QW and the barrier materials, producing a blue shift of the QW bandgap, and are annealed out. Increases in bandgap energy (measured using low temperature photoluminescence spectroscopy) of greater than 60 meV can be achieved. Absorption spectroscopy in the waveguide direction is also used to quantify any excess loss in the structure. Using a simple masking scheme to spatially modify the defect concentration, different regions of a wafer can be blue shifted by different amounts. This allows the integration of many different devices such as lasers, detectors, modulators, waveguides etc. on a single wafer using only a single, post-growth processing step. The performance of both passive (waveguide) and active (laser) devices produced using this technique is described, as well as the practicality of this technique in the production of photonic integrated circuits.

Photonic-integrated circuits and components using quantum well intermixing

The monolithic integration of optical components with different functionalities on a single semiconductor wafer requires spatially selective control of bandgap energies. We have developed a simple, post-growth technique based on quantum well intermixing using ion implantation and rapid thermal annealing, which allows multiple selective area bandgap tailoring. Waveguide absorption spectra demonstrate that the bandgap energy can be shifted as much as 90 nm without any excess loss. By depositing a SiO2 layer of different thicknesses in different regions as the implantation mask, quantum wells in different sections of a wafer can be intermixed to different degrees in a single implantation and annealing process. It has also been shown that the heavy-hole and light hole states in the quantum wells can become degenerate at a certain degree of intermixing, which allows the fabrication of polarization insensitive optical amplifiers and electro-absorptive switches. The performance of both active (laser, amplifier, modulator) and passive (waveguide) components produced using this technique will be presented.

InGaAs/InGaAsP diffused quantum wells optical amplifiers and modulators

Diffused quantum wells (DFQW) optical devices have been widely investigated for use in optical electronics integrated circuits. In this paper, we report on the performance of five-period DFQW optical amplifiers and modulators. The result show that the QW amplifiers and modulators maintain at single guiding mode operation after the QW structure has been annealed. The running range of the operation l wavelength of QW optical amplifiers is 34 meV without a significant degradation in the modal gain peak by interdiffusing the QWs. The QW interdiffusion was accomplished by P+ ion implantation to the upper region of the top cladding layer of the multilayer structure and followed by rapid thermal annealing such that the implanted ions did not damage the QW structures. The I-V characteristics of the implanted QW are similar to that of the unimplanted. Concerning the TE electro-absorptive modulation, a large contrast ratio of 35dB can be obtained at (lambda) op equals 1.55 micrometers under a small bias of -1.5V fora 500 micrometers long modulator. For TM mode, a slightly higher CR Of 37dB can be obtained at the operation wavelength although the reverse bias voltage is double.

Optical and electrical properties of bandgap shifted 1.55-/spl mu/m laser diodes

Summary form only given. In this paper we report on optical and electrical properties of 1.55-/spl mu/m InGaAsP-InP QW waveguide laser diodes blue-shifted using high-energy ion implantation and rapid thermal annealing. We demonstrate that, after shifting, waveguide losses are not increased and there is no significant change in the electrical properties of electroabsorptive modulators and laser diodes. Thus, this is a very attractive technique for achieving inexpensive and reliable photonic-integrated circuits (PIG).