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SURFACE EMITTING GaAs QUANTUM WELL LASER WITH LOW ABSORPTION DISTRIBUTED BRAGG REFLECTOR GRATINGS

IP.com Disclosure Number: IPCOM000034948D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Jaeckel, H: AUTHOR [+4]

Abstract

Surface emission in semiconductor lasers can be obtained by utilizing distributed Bragg reflector structures. Light from a semiconductor laser (SL) passes through a grating region (GR) with a periodic index modulation where a small fraction per unit length is radiated upward. In such structures the absorption in the grating region (GR) is normally very high so that the efficiency is low. Herein, a structure is disclosed in which the bandgap in the grating region (GR) is 20 - 40 meV higher than in the laser region (SL). This increases the efficiency and allows higher power operation.

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SURFACE EMITTING GaAs QUANTUM WELL LASER WITH LOW ABSORPTION DISTRIBUTED BRAGG REFLECTOR GRATINGS

Surface emission in semiconductor lasers can be obtained by utilizing distributed Bragg reflector structures. Light from a semiconductor laser (SL) passes through a grating region (GR) with a periodic index modulation where a small fraction per unit length is radiated upward. In such structures the absorption in the grating region (GR) is normally very high so that the efficiency is low. Herein, a structure is disclosed in which the bandgap in the grating region (GR) is 20 - 40 meV higher than in the laser region (SL). This increases the efficiency and allows higher power operation. GaAs quantum wells (QW) grown by molecular beam epitaxy (MBE) on ridged substrates are thicker on a narrow ridge (NR) than on a wide ridge (WR) because of surface diffusion of Ga atoms during growth, and consequently have smaller effective bandgaps. This effect is used in the design of a distributed Bragg reflector (DBR) surface emitting laser (SEL). A (100)-GaAs substrate is patterned in the (011) direction, the ridge width varying between narrow ridge (NR) and wide ridge (WR) sections, as shown in the figure. During the subsequent MBE growth of the layers forming the laser structure, a narrower bandgap laser section (SL) is formed on the narrow ridge (NR) and a wider bandgap section on the wider ridge (WR). Standard post growth processes complete the semiconductor laser (SL). On the wid...