The paper theoretically investigates the carrier transport in a thin variable-gap p-n structure in which the band gap linearly increases from the structure's interface towards Ohmic contacts. The peculiarities of minority carrier redistribution taking place in the base regions for both directions of the current are established. The influence of band-gap grading on the direct and reverse branches of current-voltage characteristics. particularly, on formation of a portion with negative differential resistance at the reverse bias is discussed. The results of calculations are illustrated for a variable-gap p-n structure based on HgCdTe solid solution. (c) 2006 Elsevier B.V All rights reserved.