P‐GaAs/p‐Ge/n‐Ge heterostructures with a submicron (0.1 &mgr;m) GaAs window for the thermophotovoltaic (TPV) application have been fabricated using the combination of LPE and Zn‐diffusion techniques. Due to the increase of the open circuit voltage by growth of a GaAs wide bandgap window, an increase of efficiency of Ge based TPV cells from 2.6 – 4.8&percent; up to 3.1 – 6.1 &percent; takes place for the emitter temperature in the range of 1400 – 1900 K. The efficiencies higher than 13&percent; under the cut‐off at &lgr;<900 nm AM0 solar spectrum have been achieved in photovoltaic (PV) concentrator cells with a GaAs window layer at photocurrent densities of 3–25 A/cm2. By means of LPE growth and Zn diffusion techniques, TPV cells based onp‐InAsSbP/n‐InAsSbP/n‐InAs structures were fabricated sensitive in the infrared range of 2.5–3.4 &mgr;m. Lattice‐matched InAsSbP (Eg=0.45–0.48eV) quaternary alloy layers were grown on the (100) InAs substrates at 850 K by the step‐cooling LPE technique. Low‐temperature (600–630 K) pseudo‐closed box Zn diffusion was used to producep‐njunctions in InAsSbP and InAs. Developed InAsSbP‐based TPV cells demonstrate rather good perfomance, which can be improved by the structure optimisation. © 2003 American Institute of Physics