Bell Telephone Laboratories

Bell Communications Research, Inc.

John M Worlock

Robert E Nahory

James Power Gordon

Martin Alan Pollack

Kathleen Kash

A semi-conductor device having the properties of carrier confinement induced by local variations of strain comprising a semi-conductor base material, a vertical confinement layer over the semi-conductor base material for vertical confining charge carriers and a strain layer which creates a local strain pattern in the underlying semi-conductor material which strain pattern laterally confines charge carriers in accordance with the strain pattern. The semi-conductor base may include a quantum-well, e.g., one formed utilizing a superlattice structure, where the charge carriers are laterally confined within the quantum well by the strain pattern.

Semiconductor devices having strain-induced lateral confinement of

A low noise multistage photodetector device is formed from a sequence of pairs of layers of opposite conductivity type having heterojunctions between each pair. The second layer of each pair has a bandgap which is larger than the bandgap of the first layer of the pair adjacent to the second layer. Electrodes are formed on the device so that voltages may be applied to reverse bias the heterojunctions formed between each pair in the sequence and to forward bias the heterojunctions formed between the second layer of one pair and the first layer of another pair. The device provides traps for one sign of carrier, which traps prevent the trapped carrier from avalanching through amplification regions of the device.

Multistage avalanche photodetector

Devices constructed according to the present invention provide low noise avalanche photodetectors. The devices are comprised of a sequence of at least four layers of semiconductor material of alternating opposed conductivity. In a first embodiment the layers form alternating homojunctions and heterojunctions at the interface between adjacent layers, and the bandgap of the layers on either side of the homojunctions decreases in the direction of the propagating signal. In another embodiment the layers form heterojunctions at the interfaces between adjacent layers; the layers are grouped into a sequence of pairs of layers where the bandgap of the two layers in each pair are substantially equal; and the bandgap of the layers in the sequence of pairs of layers decreases in the direction of the propagating signal. The effect of the structure of the multilayer device is to create traps for one sign of carrier and to prevent the trapped carrier from avalanching through amplification regions of the device.

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Fair Haven, NJ, United States of America

John M Worlock