Bell Telephone Laboratories

At&t Bell Laboratories

At&t Bell Telephone Laboratories, Incorporated

Bulusu V Dutt

Aland K Chin

Henryk Temkin

Vassilis G Keramidas

Photodiodes (10) are fabricated in a single step diffusion process which exploits the characteristic of certain acceptors to form an anomalous diffusion profile (VI) including shallow and deep fronts (VIa and b) joined by an upwardly concave segment (VIc). By performing this type of diffusion into a low-doped n.sup.- -type body (12) with a carrier concentration (VII) below that of the concave segment, a p.sup.+ --p.sup.- junction (15) is formed at the depth of the concave segment and a p.sup.- --n.sup.- junction (17) is formed at a greater depth. The zone (16) between the junctions is at least partially depleted and forms the active region of a p.sup.+ --p.sup.- --n.sup.- photodiode. Specifically described are InP:Cd photodiodes.

Method of making p-i-n photodiodes

A single heterostructure light emitting device which provides high speed and high efficiency. The device includes adjacent n- and p- regions of a mixed-crystal III-V semiconductor such as GaAlAs. A lightly-doped wide bandgap injection layer is utilized to force recombination in the more heavily-doped adjacent region. The latter region also includes a graded bandgap which allows photon recycling for high efficiency.

Light emitting device for optical switching

Photodiodes (10) are fabricated in a single step diffusion process which exploits the characteristic of certain acceptors to form an anomalous diffusion profile (VI) including shallow and deep fronts (VIa and b) joined by an upwardly concave segment (VIc). By performing this type of diffusion into a low-doped n.sup.- -type body (12) with a carrier concentration (VII) below that of the concave segment, a p.sup.+ -p.sup.- junction (15) is formed at the depth of the concave segment and a p.sup.- -n.sup.- junction (17) is formed at a greater depth. The zone (16) between the junctions is at least partially depleted and forms the active region of a p.sup.+ -p.sup.- -n.sup.- photodiode. Specifically described are InP:Cd photodiodes.

p-i-n Photodiodes

A method of liquid phase epitaxy is disclosed for growing a plurality of different layers on each of a plurality of semiconductor wafers during a single heating cycle. Each of a series of melts, each corresponding to a layer to be grown, is divided, in succession, into aliquant portions and a remainder portion. Each aliquant portion is contacted by one or more wafers, and epitaxial growth occurs as the temperature is lowered. Provision of a remainder portion enables a two-phase melt, and a wafer contacts only one distinct melt at a time. After a growth step, the next successive melt likewise is separated into aliquant portions and a remainder portion, the wafers are removed from the preceding melt chambers and placed in contact with the newly formed aliquant portions, and growth of another layer ensues from another drop in temperature. The process is repeated for each melt provided. Apparatus for carrying out the method also is described.

Liquid phase epitaxy

The occurrence of pyramidal protrusions on the surface of GaAs and GaAlAs p-n junction wafers produced by a multislice liquid phase epitaxy process is avoided by slow cooling to a specified quenching temperature or below. The pyramidal protrusions are constituted of the silicon which is the amphoteric dopant used in these semiconductors. Pyramids are not formed if the epitaxial reactor is cooled at a rate of 1.degree. Celsius to 3.degree. Celsius per minute to a temperature less than about 140.degree. Celsius before the wafers are moved to the cool portion of the reactor and then further cooled to room temperature.

Elimination of silicon pyramids from epitaxial crystals of GaAs and

Indium phosphide stoichiometry in III-V semiconductor devices is sensitive to processing conditions during liquid phase epitaxy deposition. Disclosed is a method for determining indium-to-phosphorus ratio in an n-type indium phosphide semiconductor surface layer by monitoring photoluminescence at an absorption band at or near 0.99 electron volt.

Growing community of inventors

Parsippany, NJ, United States of America

Bulusu V Dutt