Bell Telephone Laboratories

Marc Ilegems

Louis A Koszi

Bertram Schwartz

Robert Louis Hartman

Wilfried R Wagner

A buried double heterostructure laser device isdescribed. A wafer of double heterostructure material is formed into narrow mesa stripes. A native oxide coating is formed on the side walls of the mesa. Semiconductor material having an index of refraction which is closely matched to the index of the active region is deposited over the mesa structure. High resistivity polycrystalline material forms on the native oxide and monocrystalline material forms on the top of the mesa. Vertical carrier and optical confinement is achieved by the higher bandgap cladding layers of the double heterostructure configuration. The native oxide acts as an electrical insulator to confine pumping current to the mesa. The closely matched polycrystalline material confines light parallel to the junction plane and prevents excitation of higher order transverse modes. Devices have been fabricated which exhibit cw threshold currents at room temperature as low as 55 mA.

Buried double heterostructure laser device

A plurality n of double heterostructure photodiodes are coupled together by (n-1) interleaved n.sup.+ -p.sup.+ tunnel junctions to form a multi-layered integrated structure which has an open circuit photovoltage approaching the sum of the open circuit photovoltages of the individual photodiodes. In one embodiment, in which radiation to be detected is made incident normal to the layers, the absorbing layers of the photodiodes get progressively thicker away from the substrate. In a second embodiment, in which the radiation is made incident parallel to the layers, all of the absorbing layers have essentially the same thickness. In a third embodiment, in which radiation is made incident normal to the layers, the structure has a stepped configuration and all of the absorbing layers have essentially the same thickness.

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Marc Ilegems