The current-voltage characteristics of nonideal InGaAsP/InP heterostru
ctures have been studied in the temperature range 77-350 K. The featur
es observed are explained on the basis of a model of tunneling-recombi
nation currents. Changes in the charge in the surface states at the he
terojunction, which occur as a result of changes in the voltage and th
e temperature, are taken into account. The density of surface states i
s estimated. Parameters of the band diagram are found.