NOVELTY - A semiconductor device (18) comprises a group IV layer; and a nucleating layer (22) formed on the group IV layer, and including a III-V compound having at least aluminum (Al) as a group III element and at least one of arsenic (As), nitrogen (N) and antimony (Sb) as a group V element.    USE - As a semiconductor device such as electronic device e.g. an opto-electronic device such as solar cell or a light emitting diode (claimed).    ADVANTAGE - The aluminum arsenide (AlAs) nucleating layer provides improved morphology of the devices and controls the position of a p-n junction near the surface of the group IV substrate through diffusion of arsenic (As) and/or phosphorus (P) and near the bottom of the III/V structure through minimized diffusion of the group IV element. The method manufactures devices with improved morphology and controlled doping profiles of group V constituents into the group IV substrate and group IV constituents into the III/V layers. Devices fabricated by the method have very good reverse breakdown voltage characteristics as well as excellent forward bias characteristics, in addition to a smooth morphology which is ideal for the epitaxy of additional active layers above the p/n junction produced or not during the nucleation sequence. The germanium profile shows that the presence of AlAs layer reduces the out-diffusion of germanium (Ge) into bottom part of III/V layer.    DETAILED DESCRIPTION - A semiconductor device (18) comprises a group IV layer; and a nucleating layer (22) formed on the group IV layer, and including a III-V compound having at least aluminum (Al) as a group III element and at least one of arsenic (As), nitrogen (N) and antimony (Sb) as a group V element. The group IV layer has a p-n junction proximate the nucleating layer. The group IV layer is one of a p-type layer, an n-type layer and an undoped layer. The device further comprises a first III-V compound layer formed on the nucleating layer, and a second III-V compound layer formed on the first III/V compound layer. The group IV layer is a group IV substrate. The group IV substrate is a vicinal substrate that has an angle of 0-20degrees. The nucleating layer, the first III/V compound layer and the second III/V compound layer is formed by an epitaxial growth process. The nucleating layer has thickness of 1-20 monolayers. An INDEPENDENT CLAIM is included for fabricating the semiconductor structure on a group IV layer for controlling the doping profile of a p-n junction formed in a group IV substrate, involving forming a nucleating layer on the group IV layer, where the nucleating layer includes a III-V compound having at least Al as a group III element and at least one of As, N and Sb as a group V element; and forming a first III-V compound layer on the nucleating layer.    DESCRIPTION OF DRAWING(S) - The figure shows a side view of the electronic device.    Semiconductor device (18)    Germanium substrate (20)    Aluminum arsenide nucleating layer (22)    Gallium indium arsenide layer. (24)