Rca Inc.

General Electric Company

Eg&g, Inc.

Robert J McIntyre

Paul P Webb

Ramon Ubaldo Martinelli

Alexander W Lightstone

A new reach-through APD structure which includes a five-layer, double-drift-region, double-junction device, having a p.sup.+ -p-n-p.sup.- -n.sup.+ structure. The middle three layers of the new APD constitute most of the thickness of the device and are fully depleted when the device is biased to its normal operating voltage. In the present invention, only primary carriers generated in the relatively narrow first drift region are subject to the full avalanche gain, resulting in dark current and noise levels much lower than conventional reach-through APD's. The new structure can be used to fabricate integrated arrays of APD's. These arrays are more durable and easily fabricated than are prior art APD's. Additionally, the new array structure does not require segmentation or isolation of the multiplying regions of the different elements of the array, allowing arrays to be made with little or no dead space between elements.

Low-noise, reach-through, avalanche photodiodes

There is provided an n.sup.+ -p-.pi.-p.sup.+ APD having a shallow and abrupt p-n junction located about 1 to 2 .mu.m into the APD and having a p-type conductivity region containing acceptors in an uncompensated excess concentration corresponding to a dose of between about 5 and 10.times.10.sup.11 acceptors/cm.sup.2. The combination of the shallow p-n junction and the doping profile in the p-type concentration region gives rise to an electric field profile having multiplication spread substantially throughout the entire thickness of the central active region of the APD and having no drift region. The electric field profile peaks adjacent the p-n junction in a value of about 2.9.times.10.sup.5 volts/cm. The electric field profile diminishes over the distance that the p-type conductivity region extends into the APD but remains at about 1.6.times.10.sup.5 volts/cm to maintain multiplication throughout the thickness of the active region of the APD. The thickness of the APD and the multiplication region extending through the APD can be achieved with an acceptable increase in operating voltage provided that the APD has a thickness less than about 40 .mu.m.

Silicon avalanche photodiode with low multiplication noise

A photoconductive detector comprises a substrate layer of semiconductor material of a first conductivity type substantially transparent of light at the wavelength to be detected and doped sufficiently to provide ohmic contact to the photoconductive active region overlying said substrate layer. The active region comprises a body of undoped semiconductor material absorptive of light at the wavelength to be detected, having first and second major surfaces. The substrate layer serves as a first ohmic contact for the entire first major surface of the active region and a metal or metal alloy serves as a second ohmic contact overlying the entire second major surface of said active region.

Vertical photoconductive detector

A photodetector array having reflector means positioned over the low response regions between elements of the array. Light incident on the reflector means is reflected into a high response region of the array. The invention also includes a method of forming the reflector means comprising the steps of forming wedge-shaped projections on the surface of a mold, coating the projections with a reflective material, filling the space between the coated projections with a transparent material and separating the mold from the material with the reflective layer adhered to the material.

Photodetector array and a method of making same

The invention is an improved avalanche photodiode having reduced electrical noise arising from spurious surface generation of charge carriers. The avalanche photodiode includes active and neighboring regions adjacent a first surface of a semiconductor body with a gap region therebetween and a channel extending a distance into the semiconductor body from a portion of the second opposed surface opposite the gap region. A P-N junction is formed between regions of opposite conductivity type including a portion thereof over the channel. Since the dopant concentration at the junction is less over the channel, the local avalanche gain over the channel is less, thereby reducing the noise contribution from carriers generated in the gap region.

Avalanche photodiode

The invention relates to an avalanche photodetector having a charge-multiplication region which is spatially separated from the detector surfaces. This photodetector includes an absorptive region, a first region overlying the absorptive region and having a central zone which is thicker than a surrounding peripheral zone and a second region overlying the first region. The avalanche region is then restricted to the thicker central zone of the first region.

Avalanche photodetector

An n-p-.pi.-p.sup.+ Si avalanche photodiode wherein the number of acceptors introduced into a Si body to form the p-type conductivity region has been reduced and this region extends a distance greater than about 35 micrometers into the body from the surface and wherein the n-type conductivity region extends a distance into the body such that the p-n junction is less than about 10 micrometers from the surface of the body. The method of the invention comprises introducing a reduced number of acceptors into the surface of the body, diffusing the acceptors into the body a distance greater than about 35 micrometers and forming an n-type conductivity region such that the p-n junction is less than 10 micrometers from the surface of the device. APDs of the invention exhibit a k.sub.eff of about 0.006 which is a factor of greater than 2.5 less than that of typical prior art devices.

Silicon avalanche photodiode with low k.sub.eff

The invention is an APD array having a plurality of p-n junctions. The p-n junctions comprise a plurality of separate regions which extend a distance into a semiconductor body from a surface thereof and have a conductivity type opposed to that of the body. A region of the same conductivity type as that of the body extends a further distance into the body and is composed of sub-regions which overlap one another in the direction parallel to the surface of the body. The elements so formed have a more uniform avalanche gain and, because of the overlap of the sub-regions of first conductivity type, the likelihood of electric breakdown at the surface is reduced and the electrical isolation between the elements is increased. Moreover, because of the proximity of the adjacent elements the likelihood of breakdown at the junction edges is reduced.

Avalanche photodiode array

A light pipe is inserted through the cap of a light detector housing and bonded to this cap. Light from a light transmitting fiber which impinges on the external end of the light pipe is transmitted with reduced loss of light to the light detector inside the housing.

Growing community of inventors

Pointe-Claire, Canada

Robert J McIntyre