Impact on photon-assisted charge carrier transport by engineering electrodes of GaN based UV photodetectors

A scheme illustrating electrode-engineering in metal-semiconductor-metal geometry is employed for fabricating GaN-based high-performance ultraviolet photodetectors. The effect of different metal-semiconductor (Au, Ti/Al and Al) junctions on photon-assisted charge-carrier transport and the current-conduction is explored. Depending upon work function of the metals, barrier height varies which contributed towards different characteristics of the device revealing linear and non-linear behaviour of the electrical measurements from the non-rectifying and rectifying contact at the metal-semiconductor interface respectively. A maximum photoresponsivity & efficiency of 280.4 mA/W and 107.04% respectively, under 5 V applied bias in the visible-blind region was measured from the device with rectifying Au electrodes. While, the photoresponsivity values of 219 mA/W and 200 mA/W under the same bias has been achieved from devices measured with near-Ohmic contacts using Ti/Al and Al electrodes, respectively. The enhancement in detector's performance with Au electrode has been attributed to the built-in electric field as well as the presence of internal gain which can promote efficient transport of charge carriers through the metal-semiconductor interface. Thus, an approach has been adopted to enhance the photoresponsivity of the fabricated GaN-based optoelectronic devices which could be utilized for wide range of industrial, military, environmental and biological applications.