Short-period silicon/germanium (SimGen) superlattice and SiGe quantum well (QW) structures have been grown by molecular beam epitaxy (MBE) on (100)Si substrates for near (1.3 mu m) and mid-infrared (3-5 mu m; 8-12 mu m) detection. For the near IR detection - suitable for fibre optical communication within a Si integrated circuit (IC) chip - short-period Si1-xGex superlattices with period lengths of several atomic monolayers (ML; e.g. m = n = 5 ML; 1 ML-1.4 Angstrom) and 2-4 monolayers wide p-doped Ge quantum well layers separated by 20 MLs of Si and embedded in two 10-nm thick Si1-xGex layers have been grown. In the superlattice structure the zone folding effect (U. Gnutzmann, K. Clausecker, Appl. Phys. 3 (1974) 9) has been predicted to produce strong interband transitions near 0.8 eV (approximate to 1.3 mu m), in the latter one the sharp Si/Ge hetero-interfaces break the k-selection rules and strong localisation of electron and hole wave function favour a strong interband excitonic transition at 1.3 pm. This results in a rather efficient room temperature photo- and electroluminescence and in sufficient absorption. An integrated waveguide/photodetector deposited on a SIMOX (Si substrate with separation by implantation of oxygen) substrate has been fabricated and an external quantum efficiency of 11% with an impulse response time of 400 ps has been observed. For the mid IR range (3-5 mu m) highly p-doped Si/SiGe quantum well detectors have been deposited on an undoped, double-sided polished Si substrate based an hetero-internal photoemission (HIP) over the Si/SiGe barrier. The absorption and photocurrent spectra have been measured from fabricated mesa detectors at 77 K. The photoresponse spectrum of the HIP detectors is shown to be widely tunable in the technological important wavelength band 3-5 pm by choice of Ge-content, well thickness and doping level. Quantum efficiencies of similar to 1% at 4 mu m and 77 K have been achieved from SiGe HIP structures, dark currents as low as 10(-8) A/cm(2) can be obtained by modulation doping. Detectivity values of D* of 10(9) cm root Hz/W have been achieved, the quantum efficiency spectrum is considerably broader and up to a factor of 4 higher than Pt:Si at 4 pm.