A CuInSe 2 layer was grown on a ZnSe substrate by the liquid phase epitaxy (LPE) method from a Bi solution. The optimum growth conditions, namely a maximum temperature of 600°C and a cooling rate of 0.5°C min −1, resulted in the over-growth layer being of thickness 6 μm and the mixed crystal layer of thickness 4.5 μm. The flatness and crystalline quality of the layer decreased in the order of the orientations (111) Se, (100), (111) Zn and (110). The electrical properties of the layer were measured by the Hall effect after heat treatment in either Se or Zn atmospheres. The LPE wafer was fabricated into p-CuInSe 2/n-ZnSe and n-CuInSe 2/n-ZnSe heterodiodes, which were characterized using I–V and C–V characteristics, photoresponse and electron beam induced current measurements. The n-CuInSe 2/n-ZnSe heterodiode in particular showed a high photoresponse. The effects of diffusion of the component elements Cu, In and Bi into the substrate and the CuInSe 2 layer were investigated by means of cathodoluminescence, Hall-effect measurements and electron-acoustic microscopy. Bi diffused in CuInSe 2 acts as a high mobility donor.