TECHNOLOGY FOCUS - ELECTRONICS - Preferred Components: In the device (I): the first region comprises substantially elements only from group-IV; the third region comprises substantially elements only from groups III and V or groups II and VI; and the second region comprises of compounds of formula ((RE1)u(RE2)v(RE3)w(J1)x(J2)y(J3)z) (where RE1 is different from RE2 and J1 is different from J2). In the second region of the device (I): a first portion of fourth composition adjacent the first region; a second portion of fifth composition; a third portion of sixth composition separated from the first portion by the second portion and adjacent the third region, where the fifth composition is different from the fourth and sixth compositions; and the second portion comprises a first surface adjacent the first portion and a second surface adjacent the third portion and the fifth composition varies from the first portion to the third portion; and the first portion is in a first state of stress and the third portion is in a second state of stress which is different from the first state of stress. In the device (II): the rare earth layer comprises a first, second and third rare earth layer so that the composition of the first layer is different from the composition of the second layer and the lattice spacing of the first layer is different from the lattice spacing of the second layer and the first rare earth layer is adjacent the first semiconductor layer and the second rare earth layer is adjacent the second semiconductor layer and the third rare earth layer separates the first and second rare earth layers; the rare earth layer's composition changes from the first semiconductor layer to the second semiconductor layer so that the composition of the rare earth layer adjacent the first semiconductor layer is different from the composition of the rare earth layer adjacent the second semiconductor layer; the first semiconductor layer is at least one of group-IV element or alloys; at least one of element of the second semiconductor layer composition is tin; and the composition of the second semiconductor layer is group-IV, group III-V or group II-VI elements so that incident radiation is converted into electrical energy. In the device (II) the rare earth layer composition in contact with the first semiconductor layer is so that the lattice constant of the first semiconductor layer is substantially less than the lattice constant of the rare earth layer composition in contact with the first semiconductor layer or biaxial compressive strain exists between the rare earth layer and the first semiconductor layer. In the device (II) the rare earth layer composition in contact with the second semiconductor layer is so that the lattice constant of the second semiconductor layer is substantially less than the lattice constant of rare earth layer composition in contact with the second semiconductor layer or biaxial tensile strain exists between the rare earth layer and the second semiconductor layer.w = greater than or equal to 0;z = less than or equal to 5;u = greater than 0; andv, x, y = less than or equal to 5.