We investigate the interface properties of ZnSSe/GaAs heterovalent heterost
ructures, using pn heterojunction diodes. It is found that only when Ga-S b
onds are formed at the interface, the current-voltage I-V characteristic ex
hibits a negative differential resistance (NDR). The photoresponse of the I
-V characteristic suggests that the NDR originates from electron capture to
an interface states band related to the Ga-S bonds. The presence of the in
terface states is also proved by a deep-level transient spectroscopy. (C) 2
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