Abstract: A nanowire of a semiconductor material and having a uniform cross-sectional area along its length is grown using a chemical vapor deposition process. In the method, a substrate is provided, a catalyst nanoparticle is deposited on the substrate, a gaseous precursor mixture comprising a constituent element of the semiconductor material is passed over the substrate, and adatoms of the constituent element are removed from a lateral surface of the nanowire during the passing of the precursor mixture. The removing comprises passing over the substrate a gaseous etchant that forms a volatile compound with the adatoms, the gaseous etchant comprising a halogenated hydrocarbon. Removing the adatoms of the constituent element before such adatoms are incorporated into the nanowire prevents such adatoms from accumulating on the lateral surface of the nanowire and allows the nanowire to grow with a uniform cross-sectional area along its length.

Abstract: A heterojunction for a semiconductor device. The heterojunction has a first region formed from a first semiconductor material having a first conductivity type, a second region formed from a second semiconductor material having a second conductivity type, and an intermediate layer between the first region and the second region. The band line-up of the first region, the intermediate layer, and the second region has no bound states in its conduction band and no bound states in its valence band. The intermediate layer has a thickness small enough to allow electrons to tunnel from the first region to the second region with negligible attenuation. The semiconductor device may be a heterojunction bipolar transistor. The conduction band of the intermediate layer has a higher energy level than the conduction bands of the first and second regions.

Abstract: A heterojunction for a semiconductor device. The heterojunction has a first region formed from a first semiconductor material having a first conductivity type, a second region formed from a second semiconductor material having a second conductivity type, and an intermediate layer between the first region and the second region. The band line-up of the first region, the intermediate layer, and the second region has no bound states in its conduction band and no bound states in its valence band. The intermediate layer has a thickness small enough to allow electrons to tunnel from the first region to the second region with negligible attenuation. The semiconductor device may be a heterojunction bipolar transistor. The conduction band of the intermediate layer has a higher energy level than the conduction bands of the first and second regions.