Very low dark current heterojunction CCD's

A model has been formulated which accounts for the major sources of dark current (JD) associated with a single pixel of a heterojunction, Schottky gate charge-coupled device (CCD). This model predicts the temperature dependence of JDand shows that for properly fabricated gates, bulk generation in the channel is the primary source of dark current. To verify the model, the dark current of Al0.3Ga0.7As/ GaAs n-p⁺heterostructure CCD's was measured over the temperature range 23-55°C. At room temperature,J_{D} approx 83pA/cm², typically, and some pixels have JDas low as 43 pA/cm². These are the lowest dark currents reported to date for a CCD structure. The data at 55°C show that, typically, JDincreases to ∼ 1 nA/cm². Furthermore, the data confirm the temperature dependence of JDpredicted by the model.