Vertical transport I-V relations of type-I GaAs/AlAs superlattices wit
h doped wells and weak coupling between wells at 77K were investigated
with quasistatic and dynamic method. Spontaneous current oscillations
are also investigated. The domain formation time 70 +/- 30 ns is dire
ctly measured. By using discrete-tunneling model, the key parameters o
f the relation between tunneling current and the bias between adjacent
wells were quantitatively determined from the experimental data.