Abstract: 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.

Abstract: Gallium arsenide antimonide phosphide (GaAsSbP) has been successfully grown on a gallium arsenide substrate by liquid phase epitaxy. A critical amount of phosphorus initially in growth solution is depleted with consequent grading of lattice constant and bandgap in the epitaxially grown layer. The substrate and graded layer as a subassembly are well suited for use in electronic devices such as double heterostructure lasers, light-emitting diodes, Schottky barrier diodes, and p-n junction photodiodes in the near-infrared low loss region of optical fibers.