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Browse Prior Art Database

Single-sided contact laser and a method for doing the same

IP.com Disclosure Number: IPCOM000125304D
Original Publication Date: 2005-May-25
Included in the Prior Art Database: 2005-May-25
Document File: 5 page(s) / 664K

Publishing Venue

IBM

Abstract

A 10Gb/s edge-emitter DFB InP laser diode emitting at 1310 nm, and having the anode (p) and cathode (n) contacts fabricated on the same surface as the laser’s ridge was designed and fabricated. This was made possible by epitaxially incorporating a buried contact layer under the laser ridge. The buried contact layer was designed to provide a similar series resistance as is typically obtained with a backside substrate contact. High-speed small-signal and large-signal measurements of the laser diode showed good 10Gb/s operation.

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Single-sided contact laser and a method for doing the same

Device structure:

  The laser diode anode (p) and cathode (n) contacts were fabricated on the same surface as was the laser's ridge. We refer to this laser as a single-side contact laser (SSC-LD). Scanning electron microscope (SEM) cross sections of the laser are shown in Fig. 1 (a)-(b), and a detailed view of ridge region is shown in Fig. 1(c). The cross section is showing a 9.3 micron wide ridge with the n-contact made to the top n+-InGaAs layer, and p-contact made to a bottom p+-InGaAs layer. Each of the InGaAs layers is 500 nm thick. In a different version of the laser the top InGaAs film was 30 nm thick. The active region, embedded in an InP cladding material, is located at the center of the ridge, at about 3.1 micron below the n+-InGaAs layer and at about
2.5 microns above the bottom p+-InGaAs layer. The laser chip top surface is coated by an 800 nm thick SiO2 film to reduce the n-pad parasitic capacitance. The SiO2 film has an opening on the top of the ridge for the n-pad metal to make contact with the n+-InGaAs layer and another opening for the p-pad metal (bottom-left) to make contact with the p+-InGaAs layer.

  Different contact layouts were used as shown in Fig. 2. In some layouts, (d) and (e), the p-contact is made on either side of the laser ridge to further minimize the series resistance. In one design, (e), the circular n-pad is eliminated so the contact to the device is made directly to the ri...