The ZnSe/CuGaSe2 heterojunctions were fabricated by flash evaporation technique of CuGaSe2 onto the (110) surface of ZnSe crystals. CuGaSe2 layers had thickness similar to2-4 mum and showed a hole concentration up to (1.5-18.0) x 10(18) cm(-3) and mobility mu similar to 4-24 cm(2) V-1 s(-1) at 300 K. The charge carrier concentration in ZnSe crystals at 300 K was n = 5.6 x 10(16) cm(-3) and their mobility mu = 300 cm(2) V-1 s(-1). The investigated ZnSe/CuGaSe2 heterojunctions have at the inter-face an intermediate layer with a thickness of similar to450-750 Angstrom and a linear graded band gap as well as an i-ZnSe compensated layer with a thickness of similar to1-2 mum and resistivity psimilar to10(8)-10(9) Ohm cm. The i-ZnSe layer is highly compensated due to the presence of Cu acceptor impurities. In this layer the Fermi level position E-c - F(0)similar to690 meV and a trap level position E-1 - F(0)similar to17 meV were determined. The total trap concentration in the i-ZnSe layer is N(1)similar to5 x 10(14) cm(-3). The mean free path of excited charge carriers in the graded band gap region was calculated as lambdasimilar to55 Angstrom. On the basis of experimental data analysis of electrophysical properties of both ZnSe/CuGaSe2 heterojunctions and constituent materials the energetic band diagram of the investigated heterostructures is proposed. The current transport mechanism through ZnSe/CuGaSe2 heterojunctions is consequently elucidated. (C) 2002 Elsevier Science Ltd. All rights reserved.