Atomic layer deposited HfO2 based metal insulator semiconductor GaN ultraviolet photodetectors

A report on GaN based metal insulator semiconductor (MIS) ultraviolet (UV) photodetectors (PDs) with atomic layer deposited (ALD) 5-nm-thick HfO2 insulating layer is presented. Very low dark current of 2.24 × 10-11 A and increased photo to dark current contrast ratio was achieved at 10 V. It was found that the dark current was drastically reduced by seven orders of magnitude at 10 V compared to samples without HfO2 insulating layer. The observed decrease in dark current is attributed to the large barrier height which is due to introduction of HfO2 insulating layer and the calculated barrier height was obtained as 0.95 eV. The peak responsivity of HfO2 inserted device was 0.44 mA/W at bias voltage of 15 V.