Abstract: An embodiment of a radiation detector includes a semiconductor-based blocking structure interposed between the detector's absorption region and at least one of its contact structures. The blocking structure is adapted to prevent minority carriers generated within the adjacent contact structure from reaching the absorption region, and may also prevent minority carriers generated within the absorption region near the contact structure from entering the contact structure. Majority carriers, on the other hand, may be substantially unimpeded by the blocking structure in moving from the absorption region to the contact structure. In an embodiment, the blocking structure has a higher effective energy gap than its adjacent contact structure and than the absorption region. The interface between the blocking structure and the absorption region may be graded, so that the effective energy gap decreases gradually between the blocking structure and the absorption region.

Abstract: A method of forming selected Group III-nitride regions uses a masking layer to cause differential growth between single crystal Group III-nitride material and polycrystalline Group III-nitride material. The epitaxial process is chosen to provide vertical growth so as to allow for replication of the mask edges at the defined limits for the selected regions. By using an etchant that is selective between polycrystalline and single crystal Group III-nitride material, the polycrystalline material (that grew over the mask layer) can be removed, leaving only the single crystal Group III-nitride (that grew over the exposed substrate material).

Abstract: An MQW laser comprises an active region in which a multiplicity of barriers each includes a doped barrier layer separated from its adjacent quantum well layers by undoped barrier layers. In a preferred embodiment, each barrier of an InGaAsP/InP SCH MQW laser includes a p-type (e.g., Be, Mg or C) delta-doped InGaAsP barrier layer sandwiched between a pair of undoped InGaAsP barrier layers. With suitable doping concentration and thickness of the delta-doped barrier layer, we have demonstrated MQW lasers with To as high as 82 K.

Abstract: The specification describes a lift-off technique useful in the manufacture of III-V semiconductor devices such as MQW lasers. The lift-off step is improved by a spacer layer of III-V semiconductor that can be non-selectively etched to form a mesa stripe, and selectively etched for the lift-off step. The spacer layer allows the etch mask to be dimensionally adjusted to reduce or eliminate overhang of the mesa, and prevent adverse shadowing effects. MBE is effective for both growing the multilayer stack and regrowing the blocking layer. A self-aligned mask on the multilayer stack can be produced by removing the overhang, and facilitating lift-off by producing an undercut in the III-V spacer layer using selective etching.