A p-doped resonant-tunneling device with tunnel barriers having differ
ent transmission coefficients is investigated. The magneto-oscillation
s observed in the tunnel current when a quantizing magnetic field is a
pplied along the direction of current flow are used to measure the res
onant space-charge buildup in the quantum well. For one bias direction
, intrinsic bistability is observed on one of the resonant peaks in th
e current-voltage characteristics.