Breakdown behavior of AlGaN MSM UV photodetectors

GaN is an attractive wide bandgap semiconductor material for optoelectronic device applications at blue and UV wavelengths. The breakdown behavior of interdigital MSM type of AlGaN UV photodetectors (PDs) are reported here. The AlGaN was deposited using MOCVD technique. The MSM devices were fabricated using undoped AlGaN (Al composition is 0.13) epitaxial layer on sapphire substrate. Au/Ti metallization was patterned as metal electrodes on AlGaN. Very high UV responsivity of the devices was achieved at DC bias voltage in the range of 60-140V depending on the device dimensions. The breakdown voltage exhibits a negative temperature coefficient. The relationship between the breakdown voltage and device dimensions has been investigated using both of I-V, C-V characteristics. It has been found that annealing of the contact modifies the device the device characteristics, in particular, the breakdown behaviors.