A study of the dark currents of InSb charge injection devices

The dark currents of InSb metal-insulator-semiconductor (MIS) charge injection devices (CIDs) in the temperature range 30 to 120K are studied. It is found that a thermal-generating process dominates the dark current in the high temperature region. When the device is under small bias voltage, a bump in the trap emission current appears below 70K. This current is due to carrier capture and emission processes of a hole trap state located in the bulk material, and the measured activation energy is 50meV. For larger bias conditions, the band-to-band tunnelling current gradually overcomes the trap emission current. It smears out the bump in the trap emission current, and shows a slightly temperature-dependent behaviour in the plot. The effects of field electrodes are also studied. It is found from experimental results that the edge of the electric field around the device periphery plays an important role in the band-to-band tunnelling process, and a field electrode with suitable bias can improve the dark current response drastically.